Tests for evaluating nonresponse bias in surveys Section 5. Discussion

In this paper, we considered tests for nonresponse bias after poststratification or inverse propensity weighting has been used. The arguments in the theorems could be extended to similar methods that are used to adjust for nonresponse bias such as raking, which iteratively poststratifies to marginal population totals, or calibration, which adjusts the weights so that estimated population totals agree with control totals for a set of auxiliary variables. Haziza and Lesage (2016) argued that using a two-step procedure of propensity weighting followed by calibration provides more protection against nonresponse bias than using calibration alone in a single step, because single-step calibration implies a model relating the response propensities and the calibration variables and that model may be misspecified. The tests proposed in this paper could be extended to situations in which both propensity weighting and poststratification are used, or could be used separately to assess the bias removed in each step of a two-step process.

We employed the jackknife for the replication variance estimation. However, all of the estimators are smooth functions of population totals, so other replication variance estimators such as balanced repeated replication or bootstrap could be used as well.

A challenge for evaluating nonresponse bias is the limited amount of information available for the selected sample. For some surveys all available auxiliary information is used or considered for forming poststrata, raking classes, or inverse propensity weights. The poststratified estimator for characteristics used in the poststratification has no variance or bias, so testing these or closely related characteristics will not uncover nonresponse bias in other survey variables. Auxiliary variables that are not used for nonresponse adjustments are often omitted only because they were not selected in model selection method used to form the poststrata or select variables for the logistic regression, and that typically occurs because they have low explanatory power for predicting the response indicator after the other variables are included in the model. For surveys with less frame information, it may be possible to obtain auxiliary information from other sources, such as administrative records associated with the respondents’ addresses or paradata. It is important to make sure that the variables used to test nonresponse bias are recorded consistently for respondents and nonrespondents. If, for example, y MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyEaaaa@356C@  is the interviewer’s curbside assessment about whether children are present in the household, that initial assessment should be used for both respondents and nonrespondents: the assessment used in the nonresponse bias analysis should not be updated after the interviewer ascertains the actual number of children in a responding household.

After testing available variables for nonresponse bias, we still do not know whether the adjustments have removed the bias for outcome variables that are available only for the respondents. Abraham, Helms and Presser (2009) and Kohut, Keeter, Doherty, Dimock and Christian (2012) found that estimates of volunteering and civic participation are higher from surveys with low response rates than from the Current Population Survey, indicating that weighting adjustments do not remove bias for civic engagement variables although they appear to remove bias for demographic variables and home ownership. But testing a wide range of auxiliary variables for residual bias may give more confidence in the results of a survey on the untested variables, or may indicate concerns about inferences from the survey for variables of interest. We recommend that survey designers plan the survey with nonresponse bias assessment in mind, and collect additional information for the selected sample whenever possible. In general, the more information that can be collected about the selected sample, the better.

The comparison of estimates using different sets of weights may be of special interest when studying responsive or adaptive design strategies such as those described in Groves and Heeringa (2006) and summarized in Tourangeau, Brick, Lohr and Li (2016). In these, later phases of the design are modified using information gleaned in the early returns. One responsive design strategy may be to estimate response rates after the first phase of the survey, and then to allocate resources in the second phase to equalize rates across subgroups of interest. In an experimental comparison of different responsive design strategies, it may be of interest to evaluate the estimated nonresponse bias from the strategies. Riddles, Marker, Rizzo, Wiley and Zukerberg (2015) compared nonresponse-weighted estimates from different data cutoff points in the U.S. Schools and Staffing Survey, to see if estimates changed with earlier truncation of data collection.

The results in Theorems 1 through 5 are expressed for probability samples. There is increased interest in using nonprobability samples to study populations (Baker, Brick, Bates, Battaglia, Couper, Dever, Gile and Tourangeau 2013). Proponents of nonprobability samples argue that with response rates sometimes below 10%, an inexpensive large nonprobability sample can have smaller mean squared error than a small probability sample. The same methods of poststratification and inverse propensity weighting are typically used with nonprobability samples. The tests proposed in this paper can be adapted for use with nonprobability samples, provided that auxiliary information is known for a collection of individuals that can serve as a stand-in for a sampling frame. For a web survey, it might be possible to compare characteristics of persons visiting the web page with those of persons completing the survey. Further research is needed in this area.

Acknowledgements

The authors thank the reviewers for their helpful suggestions that led to improvements in the article.

Appendix

The following lemma shows that the additional variability due to the stochastic response mechanism is O( M 2 /n ). MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4tamaabm aabaWaaSGbaeaacaWGnbWaaWbaaSqabeaacaaIYaaaaaGcbaGaamOB aaaaaiaawIcacaGLPaaacaGGUaaaaa@3A4B@

Lemma 1. Suppose assumptions (A3) and (A5) are met, and that | q hik |Q MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaqWaaeaaca aMc8UaamyCamaaBaaaleaacaWGObGaamyAaiaadUgaaeqaaOGaaGPa VdGaay5bSlaawIa7aiabgsMiJkaadgfaaaa@4128@  for all ( hik )U. MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaeWaaeaaca WGObGaamyAaiaadUgaaiaawIcacaGLPaaacqGHiiIZcaWGvbGaaiOl aaaa@3BD2@  Then

E[ V( hikU Z hik w hik q hik r hik |Z ) ]=O( M 2 /n ). MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyramaadm aabaGaamOvamaabmaabaWaaqGaaeaadaaeqbqaaiaadQfadaWgaaWc baGaamiAaiaadMgacaWGRbaabeaakiaadEhadaWgaaWcbaGaamiAai aadMgacaWGRbaabeaakiaadghadaWgaaWcbaGaamiAaiaadMgacaWG RbaabeaakiaadkhadaWgaaWcbaGaamiAaiaadMgacaWGRbaabeaaae aacaWGObGaamyAaiaadUgacqGHiiIZcaWGvbaabeqdcqGHris5aaGc caGLiWoacaWHAbaacaGLOaGaayzkaaaacaGLBbGaayzxaaGaaGypai aad+eadaqadaqaamaalyaabaGaamytamaaCaaaleqabaGaaGOmaaaa aOqaaiaad6gaaaaacaGLOaGaayzkaaGaaGOlaaaa@59BD@

Proof. By assumption (A5),

| E[ V( hikU Z hik w hik q hik r hik |Z ) ] | =| E[ h=1 H i=1 N h k=1 M hi p=1 M hi Z hik Z hip w hik w hip Cov( r hik , r hip ) q hik q hip ] | Q 2 E[ h=1 H i=1 N h k=1 M hi p=1 M hi Z hik Z hip w hik w hip ] = Q 2 h=1 H i=1 N h k=1 M hi p=1 M hi P[ ( hi )S ]P[ k S hi p S hi ] w hik w hip =O( M 2 /n ). MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqbaeaabqGaaa aabaWaaqWaaeaacaaMe8UaamyramaadmaabaGaamOvamaabmaabaWa aqGaaeaadaaeqbqaaiaadQfadaWgaaWcbaGaamiAaiaadMgacaWGRb aabeaakiaadEhadaWgaaWcbaGaamiAaiaadMgacaWGRbaabeaakiaa dghadaWgaaWcbaGaamiAaiaadMgacaWGRbaabeaakiaadkhadaWgaa WcbaGaamiAaiaadMgacaWGRbaabeaaaeaacaWGObGaamyAaiaadUga cqGHiiIZcaWGvbaabeqdcqGHris5aaGccaGLiWoacaWHAbaacaGLOa GaayzkaaaacaGLBbGaayzxaaGaaGjbVdGaay5bSlaawIa7aaqaaiaa i2dadaabdaqaaiaaysW7caWGfbWaamWaaeaadaaeWbqabSqaaiaadI gacaaI9aGaaGymaaqaaiaadIeaa0GaeyyeIuoakmaaqahabeWcbaGa amyAaiaai2dacaaIXaaabaGaamOtamaaBaaameaacaWGObaabeaaa0 GaeyyeIuoakmaaqahabeWcbaGaam4Aaiaai2dacaaIXaaabaGaamyt amaaBaaameaacaWGObGaamyAaaqabaaaniabggHiLdGcdaaeWbqabS qaaiaadchacaaI9aGaaGymaaqaaiaad2eadaWgaaadbaGaamiAaiaa dMgaaeqaaaqdcqGHris5aOGaaGPaVlaadQfadaWgaaWcbaGaamiAai aadMgacaWGRbaabeaakiaadQfadaWgaaWcbaGaamiAaiaadMgacaWG WbaabeaakiaadEhadaWgaaWcbaGaamiAaiaadMgacaWGRbaabeaaki aadEhadaWgaaWcbaGaamiAaiaadMgacaWGWbaabeaakiaaboeacaqG VbGaaeODamaabmaabaGaamOCamaaBaaaleaacaWGObGaamyAaiaadU gaaeqaaOGaaGilaiaadkhadaWgaaWcbaGaamiAaiaadMgacaWGWbaa beaaaOGaayjkaiaawMcaaiaadghadaWgaaWcbaGaamiAaiaadMgaca WGRbaabeaakiaadghadaWgaaWcbaGaamiAaiaadMgacaWGWbaabeaa aOGaay5waiaaw2faaiaaysW7aiaawEa7caGLiWoaaeaaaeaacqGHKj YOcaWGrbWaaWbaaSqabeaacaaIYaaaaOGaamyramaadmaabaWaaabC aeqaleaacaWGObGaaGypaiaaigdaaeaacaWGibaaniabggHiLdGcda aeWbqabSqaaiaadMgacaaI9aGaaGymaaqaaiaad6eadaWgaaadbaGa amiAaaqabaaaniabggHiLdGcdaaeWbqabSqaaiaadUgacaaI9aGaaG ymaaqaaiaad2eadaWgaaadbaGaamiAaiaadMgaaeqaaaqdcqGHris5 aOWaaabCaeaacaWGAbWaaSbaaSqaaiaadIgacaWGPbGaam4Aaaqaba GccaWGAbWaaSbaaSqaaiaadIgacaWGPbGaamiCaaqabaGccaWG3bWa aSbaaSqaaiaadIgacaWGPbGaam4AaaqabaGccaWG3bWaaSbaaSqaai aadIgacaWGPbGaamiCaaqabaaabaGaamiCaiaai2dacaaIXaaabaGa amytamaaBaaameaacaWGObGaamyAaaqabaaaniabggHiLdaakiaawU facaGLDbaaaeaaaeaacaaI9aGaamyuamaaCaaaleqabaGaaGOmaaaa kmaaqahabeWcbaGaamiAaiaai2dacaaIXaaabaGaamisaaqdcqGHri s5aOWaaabCaeqaleaacaWGPbGaaGypaiaaigdaaeaacaWGobWaaSba aWqaaiaadIgaaeqaaaqdcqGHris5aOWaaabCaeqaleaacaWGRbGaaG ypaiaaigdaaeaacaWGnbWaaSbaaWqaaiaadIgacaWGPbaabeaaa0Ga eyyeIuoakmaaqahabaGaamiuamaadmaabaWaaeWaaeaacaWGObGaam yAaaGaayjkaiaawMcaaiabgIGiolaadofaaiaawUfacaGLDbaacaWG qbWaamWaaeaacaWGRbGaeyicI4Saam4uamaaBaaaleaacaWGObGaam yAaaqabaGccaaISaGaamiCaiabgIGiolaadofadaWgaaWcbaGaamiA aiaadMgaaeqaaaGccaGLBbGaayzxaaGaam4DamaaBaaaleaacaWGOb GaamyAaiaadUgaaeqaaOGaam4DamaaBaaaleaacaWGObGaamyAaiaa dchaaeqaaaqaaiaadchacaaI9aGaaGymaaqaaiaad2eadaWgaaadba GaamiAaiaadMgaaeqaaaqdcqGHris5aaGcbaaabaGaaGypaiaad+ea daqadaqaamaalyaabaGaamytamaaCaaaleqabaGaaGOmaaaaaOqaai aad6gaaaaacaGLOaGaayzkaaGaaGOlaaaaaaa@1956@

The last line is implied by (A3).

Proof of Theorem 1. From (2.4),

V 1 ( θ ^ )=V[ c=1 C 1 p c ( Y ^ c R Y ¯ c R ( M ^ c R M c R ) ) Y ^ SS ] MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOvamaaBa aaleaacaaIXaaabeaakmaabmaabaGafqiUdeNbaKaaaiaawIcacaGL PaaacaaI9aGaamOvamaadmaabaWaaabCaeqaleaacaWGJbGaaGypai aaigdaaeaacaWGdbaaniabggHiLdGcdaWcaaqaaiaaigdaaeaacaWG WbWaaSbaaSqaaiaadogaaeqaaaaakmaabmaabaGabmywayaajaWaa0 baaSqaaiaadogaaeaacaWGsbaaaOGaeyOeI0IabmywayaaraWaa0ba aSqaaiaadogaaeaacaWGsbaaaOWaaeWaaeaaceWGnbGbaKaadaqhaa WcbaGaam4yaaqaaiaadkfaaaGccqGHsislcaWGnbWaa0baaSqaaiaa dogaaeaacaWGsbaaaaGccaGLOaGaayzkaaaacaGLOaGaayzkaaGaey OeI0IabmywayaajaWaaSbaaSqaaiaadofacaWGtbaabeaaaOGaay5w aiaaw2faaaaa@5996@

and

V 2 ( θ ^ )=V[ c=1 C T ^ c p c ]+2Cov[ c=1 C T ^ c p c , c=1 C ( y ¯ c R Y ¯ c R ) M ^ c R p c Y ^ SS ]. MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOvamaaBa aaleaacaaIYaaabeaakmaabmaabaGafqiUdeNbaKaaaiaawIcacaGL PaaacaaI9aGaamOvamaadmaabaWaaabCaeqaleaacaWGJbGaaGypai aaigdaaeaacaWGdbaaniabggHiLdGcdaWcaaqaaiqadsfagaqcamaa BaaaleaacaWGJbaabeaaaOqaaiaadchadaWgaaWcbaGaam4yaaqaba aaaaGccaGLBbGaayzxaaGaey4kaSIaaGOmaiaaysW7caaMc8Uaae4q aiaab+gacaqG2bWaamWaaeaadaaeWbqabSqaaiaadogacaaI9aGaaG ymaaqaaiaadoeaa0GaeyyeIuoakmaalaaabaGabmivayaajaWaaSba aSqaaiaadogaaeqaaaGcbaGaamiCamaaBaaaleaacaWGJbaabeaaaa GccaaISaWaaabCaeqaleaacaWGJbGaaGypaiaaigdaaeaacaWGdbaa niabggHiLdGcdaWcaaqaamaabmaabaGabmyEayaaraWaa0baaSqaai aadogaaeaacaWGsbaaaOGaeyOeI0IabmywayaaraWaa0baaSqaaiaa dogaaeaacaWGsbaaaaGccaGLOaGaayzkaaGabmytayaajaWaa0baaS qaaiaadogaaeaacaWGsbaaaaGcbaGaamiCamaaBaaaleaacaWGJbaa beaaaaGccqGHsislceWGzbGbaKaadaWgaaWcbaGaam4uaiaadofaae qaaaGccaGLBbGaayzxaaGaaGOlaaaa@71DF@

The leading term simplifies to

V 1 ( θ ^ ) =V[ hikU Z hik w hik c=1 C δ chik { r hik p c ( y hik Y ¯ c R ) y hik } ] =V[ E[ hikU Z hik w hik c=1 C δ chik { r hik p c ( y hik Y ¯ c R ) y hik }|Z ] ] +E[ V[ hikU Z hik w hik c=1 C δ chik { r hik p c ( y hik Y ¯ c R ) y hik }|Z ] ] =V( hikU Z hik w hik e Rhik )+E[ V[ hikU Z hik w hik c=1 C δ chik r hik p c ( y hik Y ¯ c R )|Z ] ]. MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqbaeaabqGaaa aabaGaamOvamaaBaaaleaacaaIXaaabeaakmaabmaabaGafqiUdeNb aKaaaiaawIcacaGLPaaaaeaacaaI9aGaamOvamaadmaabaWaaabuae aacaWGAbWaaSbaaSqaaiaadIgacaWGPbGaam4AaaqabaGccaWG3bWa aSbaaSqaaiaadIgacaWGPbGaam4AaaqabaaabaGaamiAaiaadMgaca WGRbGaeyicI4Saamyvaaqab0GaeyyeIuoakmaaqahabaGaeqiTdq2a aSbaaSqaaiaadogacaWGObGaamyAaiaadUgaaeqaaaqaaiaadogaca aI9aGaaGymaaqaaiaadoeaa0GaeyyeIuoakmaacmaabaWaaSaaaeaa caWGYbWaaSbaaSqaaiaadIgacaWGPbGaam4AaaqabaaakeaacaWGWb WaaSbaaSqaaiaadogaaeqaaaaakmaabmaabaGaamyEamaaBaaaleaa caWGObGaamyAaiaadUgaaeqaaOGaeyOeI0IabmywayaaraWaa0baaS qaaiaadogaaeaacaWGsbaaaaGccaGLOaGaayzkaaGaeyOeI0IaamyE amaaBaaaleaacaWGObGaamyAaiaadUgaaeqaaaGccaGL7bGaayzFaa aacaGLBbGaayzxaaaabaaabaGaaGypaiaadAfadaWadaqaaiaadwea daWadaqaamaaeiaabaWaaabuaeqaleaacaWGObGaamyAaiaadUgacq GHiiIZcaWGvbaabeqdcqGHris5aOGaamOwamaaBaaaleaacaWGObGa amyAaiaadUgaaeqaaOGaam4DamaaBaaaleaacaWGObGaamyAaiaadU gaaeqaaOWaaabCaeaacqaH0oazdaWgaaWcbaGaam4yaiaadIgacaWG PbGaam4AaaqabaaabaGaam4yaiaai2dacaaIXaaabaGaam4qaaqdcq GHris5aOWaaiWaaeaadaWcaaqaaiaadkhadaWgaaWcbaGaamiAaiaa dMgacaWGRbaabeaaaOqaaiaadchadaWgaaWcbaGaam4yaaqabaaaaO WaaeWaaeaacaWG5bWaaSbaaSqaaiaadIgacaWGPbGaam4AaaqabaGc cqGHsislceWGzbGbaebadaqhaaWcbaGaam4yaaqaaiaadkfaaaaaki aawIcacaGLPaaacqGHsislcaWG5bWaaSbaaSqaaiaadIgacaWGPbGa am4AaaqabaaakiaawUhacaGL9baacaaMc8oacaGLiWoacaaMc8UaaC OwaaGaay5waiaaw2faaaGaay5waiaaw2faaaqaaaqaaiaaywW7cqGH RaWkcaWGfbWaamWaaeaacaWGwbWaamWaaeaadaabcaqaamaaqafabe WcbaGaamiAaiaadMgacaWGRbGaeyicI4Saamyvaaqab0GaeyyeIuoa kiaadQfadaWgaaWcbaGaamiAaiaadMgacaWGRbaabeaakiaadEhada WgaaWcbaGaamiAaiaadMgacaWGRbaabeaakmaaqahabaGaeqiTdq2a aSbaaSqaaiaadogacaWGObGaamyAaiaadUgaaeqaaaqaaiaadogaca aI9aGaaGymaaqaaiaadoeaa0GaeyyeIuoakmaacmaabaWaaSaaaeaa caWGYbWaaSbaaSqaaiaadIgacaWGPbGaam4AaaqabaaakeaacaWGWb WaaSbaaSqaaiaadogaaeqaaaaakmaabmaabaGaamyEamaaBaaaleaa caWGObGaamyAaiaadUgaaeqaaOGaeyOeI0IabmywayaaraWaa0baaS qaaiaadogaaeaacaWGsbaaaaGccaGLOaGaayzkaaGaeyOeI0IaamyE amaaBaaaleaacaWGObGaamyAaiaadUgaaeqaaaGccaGL7bGaayzFaa GaaGPaVdGaayjcSdGaaGPaVlaahQfaaiaawUfacaGLDbaaaiaawUfa caGLDbaaaeaaaeaacaaI9aGaamOvamaabmaabaWaaabuaeqaleaaca WGObGaamyAaiaadUgacqGHiiIZcaWGvbaabeqdcqGHris5aOGaamOw amaaBaaaleaacaWGObGaamyAaiaadUgaaeqaaOGaam4DamaaBaaale aacaWGObGaamyAaiaadUgaaeqaaOGaamyzamaaBaaaleaacaWGsbGa amiAaiaadMgacaWGRbaabeaaaOGaayjkaiaawMcaaiabgUcaRiaadw eadaWadaqaaiaadAfadaWadaqaamaaeiaabaWaaabuaeqaleaacaWG ObGaamyAaiaadUgacqGHiiIZcaWGvbaabeqdcqGHris5aOGaamOwam aaBaaaleaacaWGObGaamyAaiaadUgaaeqaaOGaam4DamaaBaaaleaa caWGObGaamyAaiaadUgaaeqaaOWaaabCaeaacqaH0oazdaWgaaWcba Gaam4yaiaadIgacaWGPbGaam4AaaqabaaabaGaam4yaiaai2dacaaI XaaabaGaam4qaaqdcqGHris5aOWaaSaaaeaacaWGYbWaaSbaaSqaai aadIgacaWGPbGaam4AaaqabaaakeaacaWGWbWaaSbaaSqaaiaadoga aeqaaaaakmaabmaabaGaamyEamaaBaaaleaacaWGObGaamyAaiaadU gaaeqaaOGaeyOeI0IabmywayaaraWaa0baaSqaaiaadogaaeaacaWG sbaaaaGccaGLOaGaayzkaaGaaGPaVdGaayjcSdGaaGPaVlaahQfaai aawUfacaGLDbaaaiaawUfacaGLDbaacaaIUaaaaaaa@3648@

Lemma 1 and Assumption (A4), which guarantees that 1/ p c MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaSGbaeaaca aIXaaabaGaamiCamaaBaaaleaacaWGJbaabeaaaaaaaa@3748@  is bounded, imply that the second term is O( M 2 /n ). MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4tamaabm aabaWaaSGbaeaacaWGnbWaaWbaaSqabeaacaaIYaaaaaGcbaGaamOB aaaaaiaawIcacaGLPaaacaGGUaaaaa@3A4B@

To show that V 2 ( θ ^ )=o( M 2 /n ), MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOvamaaBa aaleaacaaIYaaabeaakmaabmaabaGafqiUdeNbaKaaaiaawIcacaGL PaaacaaI9aGaam4BamaabmaabaWaaSGbaeaacaWGnbWaaWbaaSqabe aacaaIYaaaaaGcbaGaamOBaaaaaiaawIcacaGLPaaacaGGSaaaaa@404C@  note that by (A4) and the Cauchy-Schwarz inequality,

V[ T ^ c p c ] 1 ε 2 c=1 C d=1 C V[ ( y ¯ c R Y ¯ c R )( M ^ c R M c R ) ]V[ ( y ¯ d R Y ¯ d R )( M ^ d R M d R ) ] . MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOvamaadm aabaWaaSaaaeaaceWGubGbaKaadaWgaaWcbaGaam4yaaqabaaakeaa caWGWbWaaSbaaSqaaiaadogaaeqaaaaaaOGaay5waiaaw2faaiabgs MiJoaalaaabaGaaGymaaqaaiabew7aLnaaCaaaleqabaGaaGOmaaaa aaGcdaaeWbqabSqaaiaadogacaaI9aGaaGymaaqaaiaadoeaa0Gaey yeIuoakmaaqahabeWcbaGaamizaiaai2dacaaIXaaabaGaam4qaaqd cqGHris5aOWaaOaaaeaacaWGwbWaamWaaeaadaqadaqaaiqadMhaga qeamaaDaaaleaacaWGJbaabaGaamOuaaaakiabgkHiTiqadMfagaqe amaaDaaaleaacaWGJbaabaGaamOuaaaaaOGaayjkaiaawMcaamaabm aabaGabmytayaajaWaa0baaSqaaiaadogaaeaacaWGsbaaaOGaeyOe I0IaamytamaaDaaaleaacaWGJbaabaGaamOuaaaaaOGaayjkaiaawM caaaGaay5waiaaw2faaiaadAfadaWadaqaamaabmaabaGabmyEayaa raWaa0baaSqaaiaadsgaaeaacaWGsbaaaOGaeyOeI0Iabmywayaara Waa0baaSqaaiaadsgaaeaacaWGsbaaaaGccaGLOaGaayzkaaWaaeWa aeaaceWGnbGbaKaadaqhaaWcbaGaamizaaqaaiaadkfaaaGccqGHsi slcaWGnbWaa0baaSqaaiaadsgaaeaacaWGsbaaaaGccaGLOaGaayzk aaaacaGLBbGaayzxaaaaleqaaOGaaGOlaaaa@7300@

Assumption (A2) implies (Fuller 2009, Theorem 1.3.2) that

n [ y ¯ c R Y ¯ c R M ^ c R / M c R 1 ]N( 0, Σ c ) MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaOaaaeaaca WGUbaaleqaaOWaamWaaeaafaqabeGabaaabaGabmyEayaaraWaa0ba aSqaaiaadogaaeaacaWGsbaaaOGaeyOeI0IabmywayaaraWaa0baaS qaaiaadogaaeaacaWGsbaaaaGcbaWaaSGbaeaaceWGnbGbaKaadaqh aaWcbaGaam4yaaqaaiaadkfaaaaakeaacaWGnbWaa0baaSqaaiaado gaaeaacaWGsbaaaOGaeyOeI0IaaGymaaaaaaaacaGLBbGaayzxaaGa eyOKH4QaamOtamaabmaabaGaaCimaiaaiYcacaWHJoWaaSbaaSqaai aadogaaeqaaaGccaGLOaGaayzkaaaaaa@4DCC@

as n, MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOBaiabgk ziUkabg6HiLkaacYcaaaa@396F@  where Σ c MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaC4OdmaaBa aaleaacaWGJbaabeaaaaa@36B1@  is a non-negative definite matrix. Consequently,

( n M c R ) 2 V[ ( y ¯ c R Y ¯ c R )( M ^ c R M c R ) ] Σ c [1,1] Σ c [ 2,2 ]+2 ( Σ c [ 1,2 ] ) 2 ; MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaeWaaeaada Wcaaqaaiaad6gaaeaacaWGnbWaa0baaSqaaiaadogaaeaacaWGsbaa aaaaaOGaayjkaiaawMcaamaaCaaaleqabaGaaGOmaaaakiaadAfada WadaqaamaabmaabaGabmyEayaaraWaa0baaSqaaiaadogaaeaacaWG sbaaaOGaeyOeI0IabmywayaaraWaa0baaSqaaiaadogaaeaacaWGsb aaaaGccaGLOaGaayzkaaWaaeWaaeaaceWGnbGbaKaadaqhaaWcbaGa am4yaaqaaiaadkfaaaGccqGHsislcaWGnbWaa0baaSqaaiaadogaae aacaWGsbaaaaGccaGLOaGaayzkaaaacaGLBbGaayzxaaGaeyOKH4Qa aC4OdmaaBaaaleaacaWGJbaabeaakiaaiUfacaaIXaGaaGilaiaaig dacaaIDbGaaGjbVlaaho6adaWgaaWcbaGaam4yaaqabaGcdaWadaqa aiaaikdacaaISaGaaGOmaaGaay5waiaaw2faaiabgUcaRiaaikdada qadaqaaiaaho6adaWgaaWcbaGaam4yaaqabaGcdaWadaqaaiaaigda caaISaGaaGOmaaGaay5waiaaw2faaaGaayjkaiaawMcaamaaCaaale qabaGaaGOmaaaakiaaiUdaaaa@697C@

applying the Cauchy-Schwarz inequality to the covariance term implies that V 2 ( θ ^ )=o( M 2 /n ). MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOvamaaBa aaleaacaaIYaaabeaakmaabmaabaGafqiUdeNbaKaaaiaawIcacaGL PaaacaaI9aGaam4BamaabmaabaWaaSGbaeaacaWGnbWaaWbaaSqabe aacaaIYaaaaaGcbaGaamOBaaaaaiaawIcacaGLPaaacaGGUaaaaa@404E@

Proof of Theorem 2. We show that

V ˜ ( θ )= h=1 H n h n h 1 i S h ( b ˜ hi b ˜ h ) 2 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmOvayaaia WaaeWaaeaacqaH4oqCaiaawIcacaGLPaaacaaI9aWaaabmaeqaleaa caWGObGaaGypaiaaigdaaeaacaWGibaaniabggHiLdGcdaWcaaqaai aad6gadaWgaaWcbaGaamiAaaqabaaakeaacaWGUbWaaSbaaSqaaiaa dIgaaeqaaOGaeyOeI0IaaGymaaaadaaeqaqabSqaaiaadMgacqGHii IZcaWGtbWaaSbaaWqaaiaadIgaaeqaaaWcbeqdcqGHris5aOWaaeWa aeaaceWGIbGbaGaadaWgaaWcbaGaamiAaiaadMgaaeqaaOGaeyOeI0 IabmOyayaaiaWaaSbaaSqaaiaadIgaaeqaaaGccaGLOaGaayzkaaWa aWbaaSqabeaacaaIYaaaaaaa@5366@

is consistent, where

b ˜ hi = k S hi w hik { c=1 C 1 p c r hik δ chik ( y hik Y ¯ c R ) y hik }= k S hi w hik e ˜ rhik MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmOyayaaia WaaSbaaSqaaiaadIgacaWGPbaabeaakiaai2dadaaeqbqabSqaaiaa dUgacqGHiiIZcaWGtbWaaSbaaWqaaiaadIgacaWGPbaabeaaaSqab0 GaeyyeIuoakiaadEhadaWgaaWcbaGaamiAaiaadMgacaWGRbaabeaa kmaacmaabaWaaabCaeqaleaacaWGJbGaaGypaiaaigdaaeaacaWGdb aaniabggHiLdGcdaWcaaqaaiaaigdaaeaacaWGWbWaaSbaaSqaaiaa dogaaeqaaaaakiaadkhadaWgaaWcbaGaamiAaiaadMgacaWGRbaabe aakiabes7aKnaaBaaaleaacaWGJbGaamiAaiaadMgacaWGRbaabeaa kmaabmaabaGaamyEamaaBaaaleaacaWGObGaamyAaiaadUgaaeqaaO GaeyOeI0IabmywayaaraWaa0baaSqaaiaadogaaeaacaWGsbaaaaGc caGLOaGaayzkaaGaeyOeI0IaamyEamaaBaaaleaacaWGObGaamyAai aadUgaaeqaaaGccaGL7bGaayzFaaGaaGypamaaqafabeWcbaGaam4A aiabgIGiolaadofadaWgaaadbaGaamiAaiaadMgaaeqaaaWcbeqdcq GHris5aOGaam4DamaaBaaaleaacaWGObGaamyAaiaadUgaaeqaaOGa bmyzayaaiaWaaSbaaSqaaiaadkhacaWGObGaamyAaiaadUgaaeqaaa aa@775E@

and b ˜ h = i S h b ˜ hi / n h . MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmOyayaaia WaaSbaaSqaaiaadIgaaeqaaOGaaGypamaaqababeWcbaGaamyAaiab gIGiolaadofadaWgaaadbaGaamiAaaqabaaaleqaniabggHiLdGcda WcgaqaaiqadkgagaacamaaBaaaleaacaWGObGaamyAaaqabaaakeaa caWGUbWaaSbaaSqaaiaadIgaaeqaaaaakiaac6caaaa@4390@  Arguments in Yung and Rao (2000) then imply that ( n/ M 2 )[ V ˜ ( θ ) V ^ ( θ ) ] MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaeWaaeaada Wcgaqaaiaad6gaaeaacaWGnbWaaWbaaSqabeaacaaIYaaaaaaaaOGa ayjkaiaawMcaamaadmaabaGabmOvayaaiaWaaeWaaeaacqaH4oqCai aawIcacaGLPaaacqGHsislceWGwbGbaKaadaqadaqaaiabeI7aXbGa ayjkaiaawMcaaaGaay5waiaaw2faaaaa@43F7@  converges to zero in probability.

Note that

E[ b ˜ hi | Z ]= k S hi w hik e Rhik , MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyramaadm aabaGabmOyayaaiaWaaSbaaSqaaiaadIgacaWGPbaabeaakmaaeeaa baGaaGPaVlaahQfaaiaawEa7aaGaay5waiaaw2faaiaai2dadaaeqb qaaiaadEhadaWgaaWcbaGaamiAaiaadMgacaWGRbaabeaakiaadwga daWgaaWcbaGaamOuaiaadIgacaWGPbGaam4AaaqabaaabaGaam4Aai abgIGiolaadofadaWgaaadbaGaamiAaiaadMgaaeqaaaWcbeqdcqGH ris5aOGaaGilaaaa@4FE5@

E[ b ˜ hi 2 | Z ] =E[ ( k S hi w hik { c=1 C 1 p c [ R hik + r hik R hik ] δ chik ( y hik Y ¯ c R ) y hik } ) 2 |Z ] = ( k S hi w hik e Rhik ) 2 +V( k S hi w hik e ˜ rhik |Z ), MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqbaeaabiGaaa qaaiaadweadaWadaqaaiqadkgagaacamaaDaaaleaacaWGObGaamyA aaqaaiaaikdaaaGcdaabbaqaaiaaykW7caWHAbaacaGLhWoaaiaawU facaGLDbaaaeaacaaI9aGaamyramaadmaabaWaaqGaaeaadaqadaqa amaaqafabaGaam4DamaaBaaaleaacaWGObGaamyAaiaadUgaaeqaaa qaaiaadUgacqGHiiIZcaWGtbWaaSbaaWqaaiaadIgacaWGPbaabeaa aSqab0GaeyyeIuoakmaacmaabaWaaabCaeqaleaacaWGJbGaaGypai aaigdaaeaacaWGdbaaniabggHiLdGcdaWcaaqaaiaaigdaaeaacaWG WbWaaSbaaSqaaiaadogaaeqaaaaakmaadmaabaGaamOuamaaBaaale aacaWGObGaamyAaiaadUgaaeqaaOGaey4kaSIaamOCamaaBaaaleaa caWGObGaamyAaiaadUgaaeqaaOGaeyOeI0IaamOuamaaBaaaleaaca WGObGaamyAaiaadUgaaeqaaaGccaGLBbGaayzxaaGaeqiTdq2aaSba aSqaaiaadogacaWGObGaamyAaiaadUgaaeqaaOWaaeWaaeaacaWG5b WaaSbaaSqaaiaadIgacaWGPbGaam4AaaqabaGccqGHsislceWGzbGb aebadaqhaaWcbaGaam4yaaqaaiaadkfaaaaakiaawIcacaGLPaaacq GHsislcaWG5bWaaSbaaSqaaiaadIgacaWGPbGaam4Aaaqabaaakiaa wUhacaGL9baaaiaawIcacaGLPaaadaahaaWcbeqaaiaaikdaaaGcca aMc8oacaGLiWoacaaMc8UaaCOwaaGaay5waiaaw2faaaqaaaqaaiaa i2dadaqadaqaamaaqafabeWcbaGaam4AaiabgIGiolaadofadaWgaa adbaGaamiAaiaadMgaaeqaaaWcbeqdcqGHris5aOGaam4DamaaBaaa leaacaWGObGaamyAaiaadUgaaeqaaOGaamyzamaaBaaaleaacaWGsb GaamiAaiaadMgacaWGRbaabeaaaOGaayjkaiaawMcaamaaCaaaleqa baGaaGOmaaaakiabgUcaRiaadAfadaqadaqaamaaeiaabaWaaabuae qaleaacaWGRbGaeyicI4Saam4uamaaBaaameaacaWGObGaamyAaaqa baaaleqaniabggHiLdGccaWG3bWaaSbaaSqaaiaadIgacaWGPbGaam 4AaaqabaGcceWGLbGbaGaadaWgaaWcbaGaamOCaiaadIgacaWGPbGa am4AaaqabaaakiaawIa7aiaaykW7caWHAbaacaGLOaGaayzkaaGaaG ilaaaaaaa@AFDC@

and

E[ b ˜ h 2 |Z ] = 1 n h 2 E[ i S h b hi 2 + i S h ji b hi b hj |Z ] = 1 n h 2 i S h V ( k S hi w hik e ˜ rhik |Z )+ ( 1 n h i S h k S hi w hik e Rhik ) 2 . MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqbaeaabiGaaa qaaiaadweadaWadaqaamaaeiaabaGabmOyayaaiaWaa0baaSqaaiaa dIgaaeaacaaIYaaaaaGccaGLiWoacaaMc8UaaCOwaaGaay5waiaaw2 faaaqaaiaai2dadaWcaaqaaiaaigdaaeaacaWGUbWaa0baaSqaaiaa dIgaaeaacaaIYaaaaaaakiaadweadaWadaqaamaaqafabeWcbaGaam yAaiabgIGiolaadofadaWgaaadbaGaamiAaaqabaaaleqaniabggHi LdGccaWGIbWaa0baaSqaaiaadIgacaWGPbaabaGaaGOmaaaakiabgU caRmaaeiaabaWaaabuaeqaleaacaWGPbGaeyicI4Saam4uamaaBaaa meaacaWGObaabeaaaSqab0GaeyyeIuoakmaaqafabeWcbaGaamOAai abgcMi5kaadMgaaeqaniabggHiLdGccaWGIbWaaSbaaSqaaiaadIga caWGPbaabeaakiaadkgadaWgaaWcbaGaamiAaiaadQgaaeqaaaGcca GLiWoacaaMc8UaaCOwaaGaay5waiaaw2faaaqaaaqaaiaai2dadaWc aaqaaiaaigdaaeaacaWGUbWaa0baaSqaaiaadIgaaeaacaaIYaaaaa aakmaaqafabaGaamOvaaWcbaGaamyAaiabgIGiolaadofadaWgaaad baGaamiAaaqabaaaleqaniabggHiLdGcdaqadaqaamaaeiaabaWaaa buaeqaleaacaWGRbGaeyicI4Saam4uamaaBaaameaacaWGObGaamyA aaqabaaaleqaniabggHiLdGccaWG3bWaaSbaaSqaaiaadIgacaWGPb Gaam4AaaqabaGcceWGLbGbaGaadaWgaaWcbaGaamOCaiaadIgacaWG PbGaam4AaaqabaaakiaawIa7aiaaykW7caWHAbaacaGLOaGaayzkaa Gaey4kaSYaaeWaaeaadaWcaaqaaiaaigdaaeaacaWGUbWaaSbaaSqa aiaadIgaaeqaaaaakmaaqafabeWcbaGaamyAaiabgIGiolaadofada WgaaadbaGaamiAaaqabaaaleqaniabggHiLdGcdaaeqbqabSqaaiaa dUgacqGHiiIZcaWGtbWaaSbaaWqaaiaadIgacaWGPbaabeaaaSqab0 GaeyyeIuoakiaadEhadaWgaaWcbaGaamiAaiaadMgacaWGRbaabeaa kiaadwgadaWgaaWcbaGaamOuaiaadIgacaWGPbGaam4Aaaqabaaaki aawIcacaGLPaaadaahaaWcbeqaaiaaikdaaaGccaaIUaaaaaaa@A68F@

This implies that

E[ i S h [ b ˜ hi b ˜ h ] 2 ] =E[ i S h ( k S hi w hik e Rhik ) 2 1 n h ( i S h k S hi w hik e Rhik ) 2 ] +( 1 1 n h )E[ i S h V( k S hi w hik e ˜ rhik y hik |Z ) ], MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqbaeaabiGaaa qaaiaadweadaWadaqaamaaqafabeWcbaGaamyAaiabgIGiolaadofa daWgaaadbaGaamiAaaqabaaaleqaniabggHiLdGcdaWadaqaaiqadk gagaacamaaBaaaleaacaWGObGaamyAaaqabaGccqGHsislceWGIbGb aGaadaWgaaWcbaGaamiAaaqabaaakiaawUfacaGLDbaadaahaaWcbe qaaiaaikdaaaaakiaawUfacaGLDbaaaeaacaaI9aGaamyramaadmaa baWaaabuaeqaleaacaWGPbGaeyicI4Saam4uamaaBaaameaacaWGOb aabeaaaSqab0GaeyyeIuoakmaabmaabaWaaabuaeqaleaacaWGRbGa eyicI4Saam4uamaaBaaameaacaWGObGaamyAaaqabaaaleqaniabgg HiLdGccaWG3bWaaSbaaSqaaiaadIgacaWGPbGaam4AaaqabaGccaWG LbWaaSbaaSqaaiaadkfacaWGObGaamyAaiaadUgaaeqaaaGccaGLOa GaayzkaaWaaWbaaSqabeaacaaIYaaaaOGaeyOeI0YaaSaaaeaacaaI XaaabaGaamOBamaaBaaaleaacaWGObaabeaaaaGcdaqadaqaamaaqa fabeWcbaGaamyAaiabgIGiolaadofadaWgaaadbaGaamiAaaqabaaa leqaniabggHiLdGcdaaeqbqabSqaaiaadUgacqGHiiIZcaWGtbWaaS baaWqaaiaadIgacaWGPbaabeaaaSqab0GaeyyeIuoakiaadEhadaWg aaWcbaGaamiAaiaadMgacaWGRbaabeaakiaadwgadaWgaaWcbaGaam OuaiaadIgacaWGPbGaam4AaaqabaaakiaawIcacaGLPaaadaahaaWc beqaaiaaikdaaaaakiaawUfacaGLDbaaaeaaaeaacaaMf8Uaey4kaS YaaeWaaeaacaaIXaGaeyOeI0YaaSaaaeaacaaIXaaabaGaamOBamaa BaaaleaacaWGObaabeaaaaaakiaawIcacaGLPaaacaWGfbWaamWaae aadaaeqbqaaiaadAfadaqadaqaamaaeiaabaWaaabuaeqaleaacaWG RbGaeyicI4Saam4uamaaBaaameaacaWGObGaamyAaaqabaaaleqani abggHiLdGccaWG3bWaaSbaaSqaaiaadIgacaWGPbGaam4AaaqabaGc ceWGLbGbaGaadaWgaaWcbaGaamOCaiaadIgacaWGPbGaam4Aaaqaba GccqGHsislcaWG5bWaaSbaaSqaaiaadIgacaWGPbGaam4Aaaqabaaa kiaawIa7aiaaykW7caWHAbaacaGLOaGaayzkaaaaleaacaWGPbGaey icI4Saam4uamaaBaaameaacaWGObaabeaaaSqab0GaeyyeIuoaaOGa ay5waiaaw2faaiaaiYcaaaaaaa@AF41@

so that V ^ L ( θ ^ ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmOvayaaja WaaSbaaSqaaiaadYeaaeqaaOWaaeWaaeaacuaH4oqCgaqcaaGaayjk aiaawMcaaaaa@39AF@  is an approximately unbiased estimator of V 1 ( θ ^ ). MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOvamaaBa aaleaacaaIXaaabeaakmaabmaabaGafqiUdeNbaKaaaiaawIcacaGL PaaacaGGUaaaaa@3A3B@  The consistency follows by (A2), which implies asymptotic normality, and the law of large numbers.

Proof of Theorem 3. For cd, MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4yaiabgc Mi5kaadsgacaGGSaaaaa@38B6@

Cov[ ( y ¯ c R Y ¯ c R )( M ^ c R M c R ),( y ¯ d R Y ¯ d R )( M ^ d R M d R ) ]=o( M 2 / n 2 ) MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaae4qaiaab+ gacaqG2bWaamWaaeaadaqadaqaaiqadMhagaqeamaaDaaaleaacaWG JbaabaGaamOuaaaakiabgkHiTiqadMfagaqeamaaDaaaleaacaWGJb aabaGaamOuaaaaaOGaayjkaiaawMcaamaabmaabaGabmytayaajaWa a0baaSqaaiaadogaaeaacaWGsbaaaOGaeyOeI0IaamytamaaDaaale aacaWGJbaabaGaamOuaaaaaOGaayjkaiaawMcaaiaaiYcadaqadaqa aiqadMhagaqeamaaDaaaleaacaWGKbaabaGaamOuaaaakiabgkHiTi qadMfagaqeamaaDaaaleaacaWGKbaabaGaamOuaaaaaOGaayjkaiaa wMcaamaabmaabaGabmytayaajaWaa0baaSqaaiaadsgaaeaacaWGsb aaaOGaeyOeI0IaamytamaaDaaaleaacaWGKbaabaGaamOuaaaaaOGa ayjkaiaawMcaaaGaay5waiaaw2faaiaai2dacaWGVbWaaeWaaeaada Wcgaqaaiaad2eadaahaaWcbeqaaiaaikdaaaaakeaacaWGUbWaaWba aSqabeaacaaIYaaaaaaaaOGaayjkaiaawMcaaaaa@61D7@

because E[ ( y ¯ c R Y ¯ c R )( y ¯ d R Y ¯ d R ) ]=o( n 1 ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamyramaadm aabaWaaeWaaeaaceWG5bGbaebadaqhaaWcbaGaam4yaaqaaiaadkfa aaGccqGHsislceWGzbGbaebadaqhaaWcbaGaam4yaaqaaiaadkfaaa aakiaawIcacaGLPaaadaqadaqaaiqadMhagaqeamaaDaaaleaacaWG KbaabaGaamOuaaaakiabgkHiTiqadMfagaqeamaaDaaaleaacaWGKb aabaGaamOuaaaaaOGaayjkaiaawMcaaaGaay5waiaaw2faaiaai2da caWGVbWaaeWaaeaacaWGUbWaaWbaaSqabeaacqGHsislcaaIXaaaaa GccaGLOaGaayzkaaaaaa@4E1E@  for simple random sampling (equation (4.26) of Lohr 2010). Consequently,

V( c=1 C T ^ c p c ) = c=1 C d=1 C 1 p c 1 p d Cov[ ( y ¯ c R Y ¯ c R )( M ^ c R M c R ),( y ¯ d R Y ¯ d R )( M ^ d R M d R ) ] = c=1 C 1 p c 2 V[ y ¯ c R Y ¯ c R ]V[ M ^ c R M c R ]+o( M 2 / n 2 ). MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqbaeaabiGaaa qaaiaadAfadaqadaqaamaaqahabeWcbaGaam4yaiaai2dacaaIXaaa baGaam4qaaqdcqGHris5aOWaaSaaaeaaceWGubGbaKaadaWgaaWcba Gaam4yaaqabaaakeaacaWGWbWaaSbaaSqaaiaadogaaeqaaaaaaOGa ayjkaiaawMcaaaqaaiaai2dadaaeWbqabSqaaiaadogacaaI9aGaaG ymaaqaaiaadoeaa0GaeyyeIuoakmaaqahabeWcbaGaamizaiaai2da caaIXaaabaGaam4qaaqdcqGHris5aOWaaSaaaeaacaaIXaaabaGaam iCamaaBaaaleaacaWGJbaabeaaaaGcdaWcaaqaaiaaigdaaeaacaWG WbWaaSbaaSqaaiaadsgaaeqaaaaakiaaboeacaqGVbGaaeODamaadm aabaWaaeWaaeaaceWG5bGbaebadaqhaaWcbaGaam4yaaqaaiaadkfa aaGccqGHsislceWGzbGbaebadaqhaaWcbaGaam4yaaqaaiaadkfaaa aakiaawIcacaGLPaaadaqadaqaaiqad2eagaqcamaaDaaaleaacaWG JbaabaGaamOuaaaakiabgkHiTiaad2eadaqhaaWcbaGaam4yaaqaai aadkfaaaaakiaawIcacaGLPaaacaaISaWaaeWaaeaaceWG5bGbaeba daqhaaWcbaGaamizaaqaaiaadkfaaaGccqGHsislceWGzbGbaebada qhaaWcbaGaamizaaqaaiaadkfaaaaakiaawIcacaGLPaaadaqadaqa aiqad2eagaqcamaaDaaaleaacaWGKbaabaGaamOuaaaakiabgkHiTi aad2eadaqhaaWcbaGaamizaaqaaiaadkfaaaaakiaawIcacaGLPaaa aiaawUfacaGLDbaaaeaaaeaacaaI9aWaaabCaeqaleaacaWGJbGaaG ypaiaaigdaaeaacaWGdbaaniabggHiLdGcdaWcaaqaaiaaigdaaeaa caWGWbWaa0baaSqaaiaadogaaeaacaaIYaaaaaaakiaadAfadaWada qaaiqadMhagaqeamaaDaaaleaacaWGJbaabaGaamOuaaaakiabgkHi TiqadMfagaqeamaaDaaaleaacaWGJbaabaGaamOuaaaaaOGaay5wai aaw2faaiaadAfadaWadaqaaiqad2eagaqcamaaDaaaleaacaWGJbaa baGaamOuaaaakiabgkHiTiaad2eadaqhaaWcbaGaam4yaaqaaiaadk faaaaakiaawUfacaGLDbaacqGHRaWkcaWGVbWaaeWaaeaadaWcgaqa aiaad2eadaahaaWcbeqaaiaaikdaaaaakeaacaWGUbWaaWbaaSqabe aacaaIYaaaaaaaaOGaayjkaiaawMcaaiaai6caaaaaaa@9D37@

The second term of V 2 ( θ ^ ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOvamaaBa aaleaacaaIYaaabeaakmaabmaabaGafqiUdeNbaKaaaiaawIcacaGL Paaaaaa@398A@  is:

2Cov[ c=1 C T ^ c p c , c=1 C ( y ¯ c R Y ¯ c R ) M ^ c R p c Y ^ SS ] =2 c=1 C d=1 C 1 p c p d Cov[ T ^ c ,( y ¯ d R Y ¯ d R ) M ^ d R p d M ^ d R y ¯ d R p d Y ^ d NR ] =2 c=1 C 1 p c 2 Cov[ ( y ¯ c R Y ¯ c R )( M ^ c R M c R ),( 1 p c ) y ¯ c R M ^ c R Y ¯ c R M ^ c R p c Y ^ c NR ]+o( M 2 n 2 ) =2 c=1 C p c 1 p c 2 V[ y ¯ c R Y ¯ c R ]V[ M ^ c R M c R ]+o( M 2 n 2 ). MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrFfpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqbaeaabqqaaa aabaGaaGOmaiaaysW7caaMc8Uaae4qaiaab+gacaqG2bWaamWaaeaa daaeWbqabSqaaiaadogacaaI9aGaaGymaaqaaiaadoeaa0GaeyyeIu oakmaalaaabaGabmivayaajaWaaSbaaSqaaiaadogaaeqaaaGcbaGa amiCamaaBaaaleaacaWGJbaabeaaaaGccaaISaWaaabCaeqaleaaca WGJbGaaGypaiaaigdaaeaacaWGdbaaniabggHiLdGcdaWcaaqaamaa bmaabaGabmyEayaaraWaa0baaSqaaiaadogaaeaacaWGsbaaaOGaey OeI0IabmywayaaraWaa0baaSqaaiaadogaaeaacaWGsbaaaaGccaGL OaGaayzkaaGabmytayaajaWaa0baaSqaaiaadogaaeaacaWGsbaaaa GcbaGaamiCamaaBaaaleaacaWGJbaabeaaaaGccqGHsislceWGzbGb aKaadaWgaaWcbaGaam4uaiaadofaaeqaaaGccaGLBbGaayzxaaaaba GaaGzbVlaaywW7caaMf8UaaGzbVlaaywW7caaI9aGaaGOmamaaqaha beWcbaGaam4yaiaai2dacaaIXaaabaGaam4qaaqdcqGHris5aOWaaa bCaeqaleaacaWGKbGaaGypaiaaigdaaeaacaWGdbaaniabggHiLdGc daWcaaqaaiaaigdaaeaacaWGWbWaaSbaaSqaaiaadogaaeqaaOGaam iCamaaBaaaleaacaWGKbaabeaaaaGccaqGdbGaae4BaiaabAhadaWa daqaaiqadsfagaqcamaaBaaaleaacaWGJbaabeaakiaaiYcadaqada qaaiqadMhagaqeamaaDaaaleaacaWGKbaabaGaamOuaaaakiabgkHi TiqadMfagaqeamaaDaaaleaacaWGKbaabaGaamOuaaaaaOGaayjkai aawMcaaiqad2eagaqcamaaDaaaleaacaWGKbaabaGaamOuaaaakiab gkHiTiaadchadaWgaaWcbaGaamizaaqabaGcceWGnbGbaKaadaqhaa WcbaGaamizaaqaaiaadkfaaaGcceWG5bGbaebadaqhaaWcbaGaamiz aaqaaiaadkfaaaGccqGHsislcaWGWbWaaSbaaSqaaiaadsgaaeqaaO GabmywayaajaWaa0baaSqaaiaadsgaaeaacaWGobGaamOuaaaaaOGa ay5waiaaw2faaaqaaiaaywW7caaMf8UaaGzbVlaaywW7caaMf8UaaG ypaiaaikdadaaeWbqabSqaaiaadogacaaI9aGaaGymaaqaaiaadoea a0GaeyyeIuoakmaalaaabaGaaGymaaqaaiaadchadaqhaaWcbaGaam 4yaaqaaiaaikdaaaaaaOGaae4qaiaab+gacaqG2bWaamWaaeaacqGH sisldaqadaqaaiqadMhagaqeamaaDaaaleaacaWGJbaabaGaamOuaa aakiabgkHiTiqadMfagaqeamaaDaaaleaacaWGJbaabaGaamOuaaaa aOGaayjkaiaawMcaamaabmaabaGabmytayaajaWaa0baaSqaaiaado gaaeaacaWGsbaaaOGaeyOeI0IaamytamaaDaaaleaacaWGJbaabaGa amOuaaaaaOGaayjkaiaawMcaaiaaiYcadaqadaqaaiaaigdacqGHsi slcaWGWbWaaSbaaSqaaiaadogaaeqaaaGccaGLOaGaayzkaaGabmyE ayaaraWaa0baaSqaaiaadogaaeaacaWGsbaaaOGabmytayaajaWaa0 baaSqaaiaadogaaeaacaWGsbaaaOGaeyOeI0IabmywayaaraWaa0ba aSqaaiaadogaaeaacaWGsbaaaOGabmytayaajaWaa0baaSqaaiaado gaaeaacaWGsbaaaOGaeyOeI0IaamiCamaaBaaaleaacaWGJbaabeaa kiqadMfagaqcamaaDaaaleaacaWGJbaabaGaamOtaiaadkfaaaaaki aawUfacaGLDbaacqGHRaWkcaWGVbWaaeWaaeaadaWcaaqaaiaad2ea daahaaWcbeqaaiaaikdaaaaakeaacaWGUbWaaWbaaSqabeaacaaIYa aaaaaaaOGaayjkaiaawMcaaaqaaiaaywW7caaMf8UaaGzbVlaaywW7 caaMf8UaaGypaiaaikdadaaeWbqabSqaaiaadogacaaI9aGaaGymaa qaaiaadoeaa0GaeyyeIuoakmaalaaabaGaamiCamaaBaaaleaacaWG JbaabeaakiabgkHiTiaaigdaaeaacaWGWbWaa0baaSqaaiaadogaae aacaaIYaaaaaaakiaadAfadaWadaqaaiqadMhagaqeamaaDaaaleaa caWGJbaabaGaamOuaaaakiabgkHiTiqadMfagaqeamaaDaaaleaaca WGJbaabaGaamOuaaaaaOGaay5waiaaw2faaiaadAfadaWadaqaaiqa d2eagaqcamaaDaaaleaacaWGJbaabaGaamOuaaaakiabgkHiTiaad2 eadaqhaaWcbaGaam4yaaqaaiaadkfaaaaakiaawUfacaGLDbaacqGH RaWkcaWGVbWaaeWaaeaadaWcaaqaaiaad2eadaahaaWcbeqaaiaaik daaaaakeaacaWGUbWaaWbaaSqabeaacaaIYaaaaaaaaOGaayjkaiaa wMcaaiaai6caaaaaaa@1245@

Combining the terms,

V 2 ( θ ^ )= c 2 p c 1 p c 2 V[ y ¯ c R Y ¯ c R ]V[ M ^ c R M c R ]+o( M 2 n 2 ). MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOvamaaBa aaleaacaaIYaaabeaakmaabmaabaGafqiUdeNbaKaaaiaawIcacaGL PaaacaaI9aWaaabuaeqaleaacaWGJbaabeqdcqGHris5aOWaaSaaae aacaaIYaGaamiCamaaBaaaleaacaWGJbaabeaakiabgkHiTiaaigda aeaacaWGWbWaa0baaSqaaiaadogaaeaacaaIYaaaaaaakiaadAfada WadaqaaiqadMhagaqeamaaDaaaleaacaWGJbaabaGaamOuaaaakiab gkHiTiqadMfagaqeamaaDaaaleaacaWGJbaabaGaamOuaaaaaOGaay 5waiaaw2faaiaadAfadaWadaqaaiqad2eagaqcamaaDaaaleaacaWG JbaabaGaamOuaaaakiabgkHiTiaad2eadaqhaaWcbaGaam4yaaqaai aadkfaaaaakiaawUfacaGLDbaacqGHRaWkcaWGVbWaaeWaaeaadaWc aaqaaiaad2eadaahaaWcbeqaaiaaikdaaaaakeaacaWGUbWaaWbaaS qabeaacaaIYaaaaaaaaOGaayjkaiaawMcaaiaai6caaaa@5F9B@

We can estimate p c MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiCamaaBa aaleaacaWGJbaabeaaaaa@3677@  by the empirical response rate in poststratum c, MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4yaiaacY caaaa@3606@   V[ y ¯ c R Y ¯ c R ] MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOvamaadm aabaGabmyEayaaraWaa0baaSqaaiaadogaaeaacaWGsbaaaOGaeyOe I0IabmywayaaraWaa0baaSqaaiaadogaaeaacaWGsbaaaaGccaGLBb Gaayzxaaaaaa@3E20@  by s c 2 / n c R , MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaSGbaeaaca WGZbWaa0baaSqaaiaadogaaeaacaaIYaaaaaGcbaGaamOBamaaDaaa leaacaWGJbaabaGaamOuaaaaaaGccaGGSaaaaa@3AF0@  and, under simple random sampling, V[ M ^ c R M c R ]= M c p c ( M M c p c )/n . MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOvamaadm aabaGabmytayaajaWaa0baaSqaaiaadogaaeaacaWGsbaaaOGaeyOe I0IaamytamaaDaaaleaacaWGJbaabaGaamOuaaaaaOGaay5waiaaw2 faaiaai2dadaWcgaqaaiaad2eadaWgaaWcbaGaam4yaaqabaGccaWG WbWaaSbaaSqaaiaadogaaeqaaOWaaeWaaeaacaWGnbGaeyOeI0Iaam ytamaaBaaaleaacaWGJbaabeaakiaadchadaWgaaWcbaGaam4yaaqa baaakiaawIcacaGLPaaaaeaacaWGUbaaaiaac6caaaa@4B98@  The term V 2 ( θ ^ ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOvamaaBa aaleaacaaIYaaabeaakmaabmaabaGafqiUdeNbaKaaaiaawIcacaGL Paaaaaa@398A@  can be negative when p c <1/2 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiCamaaBa aaleaacaWGJbaabeaakiaaiYdadaWcgaqaaiaaigdaaeaacaaIYaaa aaaa@38D4@  for some poststrata; however, when p c <1/2 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamiCamaaBa aaleaacaWGJbaabeaakiaaiYdadaWcgaqaaiaaigdaaeaacaaIYaaa aaaa@38D4@  and V[ y ¯ c R ]>0, MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOvamaadm aabaGabmyEayaaraWaa0baaSqaaiaadogaaeaacaWGsbaaaaGccaGL BbGaayzxaaGaaGOpaiaaicdacaGGSaaaaa@3C79@  then the first-order term of the variance, V 1 ( θ ^ ), MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOvamaaBa aaleaacaaIXaaabeaakmaabmaabaGafqiUdeNbaKaaaiaawIcacaGL PaaacaGGSaaaaa@3A39@  is positive and the second-order term has lower order.

Proof of Theorem 4. Condition (A4) guarantees that, asymptotically, complete separation will not occur and R hik M MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOuamaaDa aaleaacaWGObGaamyAaiaadUgaaeaacaWGnbaaaaaa@390F@  is bounded away from 0.

The derivative of A ^ MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqr=fFD0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabCyqayaaja aaaa@3548@  with respect to the parameters is

D ^ ( r,β,θ ) = A ^ ( β,θ ) =[ hikS w hik [ 1+exp( x hik β ) ] 2 exp( x hik β ) x hik x hik 0 hikS w hik r hik y hik exp( x hik β ) x hik 1 ]. MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrFfpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqbaeaabiGaaa qaaiqahseagaqcamaabmaabaGaaCOCaiaaiYcacaWHYoGaaGilaiab eI7aXbGaayjkaiaawMcaaaqaaiaai2dadaWcaaqaaiabgkGi2kqahg eagaqcaaqaaiabgkGi2oaabmaabaGaaCOSdiaaiYcacqaH4oqCaiaa wIcacaGLPaaadaahaaWcbeqaaOGamai2gkdiIcaaaaaabaaabaGaaG ypamaadmaabaqbaeqabiGaaaqaaiabgkHiTmaaqafabaGaam4Damaa BaaaleaacaWGObGaamyAaiaadUgaaeqaaaqaaiaadIgacaWGPbGaam 4AaiabgIGiolaadofaaeqaniabggHiLdGcdaWadaqaaiaaigdacqGH RaWkciGGLbGaaiiEaiaacchadaqadaqaaiabgkHiTiaahIhadaqhaa WcbaGaamiAaiaadMgacaWGRbaabaGcdaahaaadbeqaaKqzGfGamai2 gkdiIcaaaaGccaWHYoaacaGLOaGaayzkaaaacaGLBbGaayzxaaWaaW baaSqabeaacqGHsislcaaIYaaaaOGaciyzaiaacIhacaGGWbWaaeWa aeaacqGHsislcaWH4bWaa0baaSqaaiaadIgacaWGPbGaam4AaaqaaO WaaWbaaWqabeaajugybiadaITHYaIOaaaaaOGaaCOSdaGaayjkaiaa wMcaaiaahIhadaWgaaWcbaGaamiAaiaadMgacaWGRbaabeaakiaahI hadaqhaaWcbaGaamiAaiaadMgacaWGRbaabaGcdaahaaadbeqaaKqz GfGamai2gkdiIcaaaaaakeaacaWHWaaabaGaeyOeI0Yaaabuaeqale aacaWGObGaamyAaiaadUgacqGHiiIZcaWGtbaabeqdcqGHris5aOGa am4DamaaBaaaleaacaWGObGaamyAaiaadUgaaeqaaOGaamOCamaaBa aaleaacaWGObGaamyAaiaadUgaaeqaaOGaamyEamaaBaaaleaacaWG ObGaamyAaiaadUgaaeqaaOGaciyzaiaacIhacaGGWbWaaeWaaeaacq GHsislcaWH4bWaa0baaSqaaiaadIgacaWGPbGaam4AaaqaaOWaaWba aWqabeaajugybiadaITHYaIOaaaaaOGaaCOSdaGaayjkaiaawMcaai aahIhadaqhaaWcbaGaamiAaiaadMgacaWGRbaabaGcdaahaaadbeqa aKqzGfGamai2gkdiIcaaaaaakeaacqGHsislcaaIXaaaaaGaay5wai aaw2faaiaai6caaaaaaa@B3A3@

Using successive conditioning and the independence of r MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrFfpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaCOCaaaa@3517@  and Z, MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrFfpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaCOwaiaacY caaaa@35AF@  the expected value of D ^ ( r,β,θ ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrFfpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabCirayaaja WaaeWaaeaacaWHYbGaaGilaiaahk7acaaISaGaeqiUdehacaGLOaGa ayzkaaaaaa@3BDD@  is

D( R,β,θ ) =[ hikU [ 1+exp( x hik β ) ] 2 exp( x hik β ) x hik x hik 0 hikU R hik y hik exp( x hik β ) x hik 1 ] =[ X [ I+Q ] 2 QX 0 T QX 1 ]. MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrpgpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqbaeaabiGaaa qaaiaahseadaqadaqaaiaahkfacaaISaGaaCOSdiaaiYcacqaH4oqC aiaawIcacaGLPaaaaeaacaaI9aWaamWaaeaafaqabeGacaaabaGaey OeI0YaaabuaeqaleaacaWGObGaamyAaiaadUgacqGHiiIZcaWGvbaa beqdcqGHris5aOWaamWaaeaacaaIXaGaey4kaSIaciyzaiaacIhaca GGWbWaaeWaaeaacqGHsislcaWH4bWaa0baaSqaaiaadIgacaWGPbGa am4AaaqaaOWaaWbaaWqabeaajugybiadaITHYaIOaaaaaOGaaCOSda GaayjkaiaawMcaaaGaay5waiaaw2faamaaCaaaleqabaGaeyOeI0Ia aGOmaaaakiGacwgacaGG4bGaaiiCamaabmaabaGaeyOeI0IaaCiEam aaDaaaleaacaWGObGaamyAaiaadUgaaeaakmaaCaaameqabaqcLbwa cWaGyBOmGikaaaaakiaahk7aaiaawIcacaGLPaaacaWH4bWaaSbaaS qaaiaadIgacaWGPbGaam4AaaqabaGccaWH4bWaa0baaSqaaiaadIga caWGPbGaam4AaaqaaOWaaWbaaWqabeaajugybiadaITHYaIOaaaaaa GcbaGaaCimaaqaaiabgkHiTmaaqafabeWcbaGaamiAaiaadMgacaWG RbGaeyicI4Saamyvaaqab0GaeyyeIuoakiaadkfadaWgaaWcbaGaam iAaiaadMgacaWGRbaabeaakiaadMhadaWgaaWcbaGaamiAaiaadMga caWGRbaabeaakiGacwgacaGG4bGaaiiCamaabmaabaGaeyOeI0IaaC iEamaaDaaaleaacaWGObGaamyAaiaadUgaaeaakmaaCaaameqabaqc LbwacWaGyBOmGikaaaaakiaahk7aaiaawIcacaGLPaaacaWH4bWaa0 baaSqaaiaadIgacaWGPbGaam4AaaqaaOWaaWbaaWqabeaajugybiad aITHYaIOaaaaaaGcbaGaeyOeI0IaaGymaaaaaiaawUfacaGLDbaaae aaaeaacaaI9aWaamWaaeaafaqabeGacaaabaGaeyOeI0IabCiwayaa faWaamWaaeaacaWHjbGaey4kaSIaaCyuaaGaay5waiaaw2faamaaCa aaleqabaGaeyOeI0IaaGOmaaaakiaahgfacaWHybaabaGaaCimaaqa aiabgkHiTiqahsfagaqbaiaahgfacaWHybaabaGaeyOeI0IaaGymaa aaaiaawUfacaGLDbaacaaIUaaaaaaa@B15F@

Also, Cov[ vec D ^ ( r,β,θ ) ]=O( M 2 /n ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrFfpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaae4qaiaab+ gacaqG2bWaamWaaeaacaqG2bGaaeyzaiaabogaceWHebGbaKaadaqa daqaaiaahkhacaaISaGaaCOSdiaaiYcacqaH4oqCaiaawIcacaGLPa aaaiaawUfacaGLDbaacaaI9aGaam4tamaabmaabaWaaSGbaeaacaWG nbWaaWbaaSqabeaacaaIYaaaaaGcbaGaamOBaaaaaiaawIcacaGLPa aaaaa@4939@  because

V[ hikS w hik r hik y hik exp( x hik β ) x hik ] =V[ hikS w hik R hik y hik exp( x hik β ) x hik ] +E{ V[ hikS w hik r hik y hik exp( x hik β ) x hik |Z ] }. MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrFfpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqbaeaabiGaaa qaaiaadAfadaWadaqaamaaqafabeWcbaGaamiAaiaadMgacaWGRbGa eyicI4Saam4uaaqab0GaeyyeIuoakiaadEhadaWgaaWcbaGaamiAai aadMgacaWGRbaabeaakiaadkhadaWgaaWcbaGaamiAaiaadMgacaWG RbaabeaakiaadMhadaWgaaWcbaGaamiAaiaadMgacaWGRbaabeaaki GacwgacaGG4bGaaiiCamaabmaabaGaeyOeI0IaaCiEamaaDaaaleaa caWGObGaamyAaiaadUgaaeaakmaaCaaameqabaqcLbwacWaGyBOmGi kaaaaakiaahk7aaiaawIcacaGLPaaacaWH4bWaa0baaSqaaiaadIga caWGPbGaam4AaaqaaOWaaWbaaWqabeaajugybiadaITHYaIOaaaaaa GccaGLBbGaayzxaaaabaGaaGypaiaadAfadaWadaqaamaaqafabeWc baGaamiAaiaadMgacaWGRbGaeyicI4Saam4uaaqab0GaeyyeIuoaki aadEhadaWgaaWcbaGaamiAaiaadMgacaWGRbaabeaakiaadkfadaWg aaWcbaGaamiAaiaadMgacaWGRbaabeaakiaadMhadaWgaaWcbaGaam iAaiaadMgacaWGRbaabeaakiGacwgacaGG4bGaaiiCamaabmaabaGa eyOeI0IaaCiEamaaDaaaleaacaWGObGaamyAaiaadUgaaeaakmaaCa aameqabaqcLbwacWaGyBOmGikaaaaakiaahk7aaiaawIcacaGLPaaa caWH4bWaa0baaSqaaiaadIgacaWGPbGaam4AaaqaaOWaaWbaaWqabe aajugybiadaITHYaIOaaaaaaGccaGLBbGaayzxaaaabaaabaGaaGzb VlabgUcaRiaadweadaGadaqaaiaadAfadaWadaqaamaaeiaabaWaaa buaeqaleaacaWGObGaamyAaiaadUgacqGHiiIZcaWGtbaabeqdcqGH ris5aOGaam4DamaaBaaaleaacaWGObGaamyAaiaadUgaaeqaaOGaam OCamaaBaaaleaacaWGObGaamyAaiaadUgaaeqaaOGaamyEamaaBaaa leaacaWGObGaamyAaiaadUgaaeqaaOGaciyzaiaacIhacaGGWbWaae WaaeaacqGHsislcaWH4bWaa0baaSqaaiaadIgacaWGPbGaam4Aaaqa aOWaaWbaaWqabeaajugybiadaITHYaIOaaaaaOGaaCOSdaGaayjkai aawMcaaiaahIhadaqhaaWcbaGaamiAaiaadMgacaWGRbaabaGcdaah aaadbeqaaKqzGfGamai2gkdiIcaaaaaakiaawIa7aiaahQfaaiaawU facaGLDbaaaiaawUhacaGL9baacaaIUaaaaiaaiccaaaa@C382@

The first term is O( M 2 /n ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrFfpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4tamaabm aabaWaaSGbaeaacaWGnbWaaWbaaSqabeaacaaIYaaaaaGcbaGaamOB aaaaaiaawIcacaGLPaaaaaa@3947@  by standard arguments and the second term is O( M 2 /n ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrFfpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4tamaabm aabaWaaSGbaeaacaWGnbWaaWbaaSqabeaacaaIYaaaaaGcbaGaamOB aaaaaiaawIcacaGLPaaaaaa@3947@  by Lemma 1, noting that the boundedness of R hik MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrFfpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOuamaaBa aaleaacaWGObGaamyAaiaadUgaaeqaaaaa@37EA@  and x hik MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrFfpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaCiEamaaBa aaleaacaWGObGaamyAaiaadUgaaeqaaaaa@3814@  also bound exp( x hik β ). MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrFfpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaciyzaiaacI hacaGGWbWaaeWaaeaacqGHsislcaWH4bWaa0baaSqaaiaadIgacaWG PbGaam4AaaqaaOWaaWbaaWqabeaajugybiadaITHYaIOaaaaaOGaaC OSdaGaayjkaiaawMcaaiaac6caaaa@4347@  Consequently,

V[ β ^ β θ ^ θ ]=D ( R,β,θ ) 1 V[ hikS w hik u( y hik , x hik , r hik ,β ) ]D ( R,β,θ ) T +o( M 2 /n ). MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrFfpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOvamaadm aabaqbaeqabiqaaaqaaiqahk7agaqcaiabgkHiTiaahk7aaeaacuaH 4oqCgaqcaiabgkHiTiabeI7aXbaaaiaawUfacaGLDbaacaaI9aGaaC iramaabmaabaGaaCOuaiaaiYcacaWHYoGaaGilaiabeI7aXbGaayjk aiaawMcaamaaCaaaleqabaGaeyOeI0IaaGymaaaakiaadAfadaWada qaamaaqafabeWcbaGaamiAaiaadMgacaWGRbGaeyicI4Saam4uaaqa b0GaeyyeIuoakiaadEhadaWgaaWcbaGaamiAaiaadMgacaWGRbaabe aakiaahwhadaqadaqaaiaadMhadaWgaaWcbaGaamiAaiaadMgacaWG RbaabeaakiaaiYcacaWH4bWaaSbaaSqaaiaadIgacaWGPbGaam4Aaa qabaGccaaISaGaamOCamaaBaaaleaacaWGObGaamyAaiaadUgaaeqa aOGaaGilaiaahk7aaiaawIcacaGLPaaaaiaawUfacaGLDbaacaWHeb WaaeWaaeaacaWHsbGaaGilaiaahk7acaaISaGaeqiUdehacaGLOaGa ayzkaaWaaWbaaSqabeaacqGHsislcaWGubaaaOGaey4kaSIaam4Bam aabmaabaWaaSGbaeaacaWGnbWaaWbaaSqabeaacaaIYaaaaaGcbaGa amOBaaaaaiaawIcacaGLPaaacaaIUaaaaa@7980@

The result in (3.3) follows because

[ D( R,β,θ ) ] 1 =[ C 0 T QXC 1 ]. MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiFu0Je9sqqrpepC0xbbL8F4rqqrFfpC0xd9Wqpe0dd9 qqaqFeFr0xbbG8FaYPYRWFb9fi0lXxbvc9Ff0dfrpm0dXdHqps0=vr 0=vr0=fdbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaamWaaeaaca WHebWaaeWaaeaacaWHsbGaaGilaiaahk7acaaISaGaeqiUdehacaGL OaGaayzkaaaacaGLBbGaayzxaaWaaWbaaSqabeaacqGHsislcaaIXa aaaOGaaGypamaadmaabaqbaeqabiGaaaqaaiabgkHiTiaahoeaaeaa caWHWaaabaGabCivayaafaGaaCyuaiaahIfacaWHdbaabaGaeyOeI0 IaaGymaaaaaiaawUfacaGLDbaacaaIUaaaaa@4A88@

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