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- 31. On the definition and interpretation of interviewer variability for a complex sampling design ArchivedArticles and reports: 12-001-X200900110886Description:
Interviewer variability is a major component of variability of survey statistics. Different strategies related to question formatting, question phrasing, interviewer training, interviewer workload, interviewer experience and interviewer assignment are employed in an effort to reduce interviewer variability. The traditional formula for measuring interviewer variability, commonly referred to as the interviewer effect, is given by ieff := deff_int = 1 + (n bar sub int - 1) rho sub int, where rho sub int and n bar sub int are the intra-interviewer correlation and the simple average of the interviewer workloads, respectively. In this article, we provide a model-assisted justification of this well-known formula for equal probability of selection methods (epsem) with no spatial clustering in the sample and equal interviewer workload. However, spatial clustering and unequal weighting are both very common in large scale surveys. In the context of a complex sampling design, we obtain an appropriate formula for the interviewer variability that takes into consideration unequal probability of selection and spatial clustering. Our formula provides a more accurate assessment of interviewer effects and thus is helpful in allocating more reasonable amount of funds to control the interviewer variability. We also propose a decomposition of the overall effect into effects due to weighting, spatial clustering and interviewers. Such a decomposition is helpful in understanding ways to reduce total variance by different means.
Release date: 2009-06-22 - Articles and reports: 12-001-X200900110887Description:
Many survey organisations focus on the response rate as being the quality indicator for the impact of non-response bias. As a consequence, they implement a variety of measures to reduce non-response or to maintain response at some acceptable level. However, response rates alone are not good indicators of non-response bias. In general, higher response rates do not imply smaller non-response bias. The literature gives many examples of this (e.g., Groves and Peytcheva 2006, Keeter, Miller, Kohut, Groves and Presser 2000, Schouten 2004).
We introduce a number of concepts and an indicator to assess the similarity between the response and the sample of a survey. Such quality indicators, which we call R-indicators, may serve as counterparts to survey response rates and are primarily directed at evaluating the non-response bias. These indicators may facilitate analysis of survey response over time, between various fieldwork strategies or data collection modes. We apply the R-indicators to two practical examples.
Release date: 2009-06-22 - 33. Stratified balanced sampling ArchivedArticles and reports: 12-001-X200900110888Description:
In the selection of a sample, a current practice is to define a sampling design stratified on subpopulations. This reduces the variance of the Horvitz-Thompson estimator in comparison with direct sampling if the strata are highly homogeneous with respect to the variable of interest. If auxiliary variables are available for each individual, sampling can be improved through balanced sampling within each stratum, and the Horvitz-Thompson estimator will be more precise if the auxiliary variables are strongly correlated with the variable of interest. However, if the sample allocation is small in some strata, balanced sampling will be only very approximate. In this paper, we propose a method of selecting a sample that is balanced across the entire population while maintaining a fixed allocation within each stratum. We show that in the important special case of size-2 sampling in each stratum, the precision of the Horvitz-Thompson estimator is improved if the variable of interest is well explained by balancing variables over the entire population. An application to rotational sampling is also presented.
Release date: 2009-06-22
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Analysis (32)
Analysis (32) (0 to 10 of 32 results)
- Articles and reports: 12-001-X200900211036Description:
Surveys are frequently required to produce estimates for subpopulations, sometimes for a single subpopulation and sometimes for several subpopulations in addition to the total population. When membership of a rare subpopulation (or domain) can be determined from the sampling frame, selecting the required domain sample size is relatively straightforward. In this case the main issue is the extent of oversampling to employ when survey estimates are required for several domains and for the total population. Sampling and oversampling rare domains whose members cannot be identified in advance present a major challenge. A variety of methods has been used in this situation. In addition to large-scale screening, these methods include disproportionate stratified sampling, two-phase sampling, the use of multiple frames, multiplicity sampling, panel surveys, and the use of multi-purpose surveys. This paper illustrates the application of these methods in a range of social surveys.
Release date: 2009-12-23 - Articles and reports: 12-001-X200900211037Description:
Randomized response strategies, which have originally been developed as statistical methods to reduce nonresponse as well as untruthful answering, can also be applied in the field of statistical disclosure control for public use microdata files. In this paper a standardization of randomized response techniques for the estimation of proportions of identifying or sensitive attributes is presented. The statistical properties of the standardized estimator are derived for general probability sampling. In order to analyse the effect of different choices of the method's implicit "design parameters" on the performance of the estimator we have to include measures of privacy protection in our considerations. These yield variance-optimum design parameters given a certain level of privacy protection. To this end the variables have to be classified into different categories of sensitivity. A real-data example applies the technique in a survey on academic cheating behaviour.
Release date: 2009-12-23 - Articles and reports: 11-522-X200800010959Description:
The Unified Enterprise Survey (UES) at Statistics Canada is an annual business survey that unifies more than 60 surveys from different industries. Two types of collection follow-up score functions are currently used in the UES data collection. The objective of using a score function is to maximize the economically weighted response rates of the survey in terms of the primary variables of interest, under the constraint of a limited follow-up budget. Since the two types of score functions are based on different methodologies, they could have different impacts on the final estimates.
This study generally compares the two types of score functions based on the collection data obtained from the two recent years. For comparison purposes, this study applies each score function method to the same data respectively and computes various estimates of the published financial and commodity variables, their deviation from the true pseudo value and their mean square deviation, based on each method. These estimates of deviation and mean square deviation based on each method are then used to measure the impact of each score function on the final estimates of the financial and commodity variables.
Release date: 2009-12-03 - 4. Evaluation and treatment of non-response in the ELFE cohort: Results of the pilot studies ArchivedArticles and reports: 11-522-X200800010960Description:
Non-response is inevitable in any survey, despite all the effort put into reducing it at the various stages of the survey. In particular, non-response can cause bias in the estimates. In addition, non-response is an especially serious problem in longitudinal studies because the sample shrinks over time. France's ELFE (Étude Longitudinale Française depuis l'Enfance) is a project that aims to track 20,000 children from birth to adulthood using a multidisciplinary approach. This paper is based on the results of the initial pilot studies conducted in 2007 to test the survey's feasibility and acceptance. The participation rates are presented (response rate, non-response factors) along with a preliminary description of the non-response treatment methods being considered.
Release date: 2009-12-03 - Articles and reports: 11-522-X200800010962Description:
The ÉLDEQ initiated a special data gathering project in March 2008 with the collection of biological materials from 1,973 families. During a typical visit, a nurse collects a blood or saliva sample from the selected child, makes a series of measurements (anthropometry, pulse rate and blood pressure) and administers questionnaires. Planned and supervised by the Institut de la Statistique du Québec (ISQ) and the Université de Montréal, the study is being conducted in cooperation with two private firms and a number of hospitals. This article examines the choice of collection methods, the division of effort among the various players, the sequence of communications and contacts with respondents, the tracing of families who are not contacted, and follow-up on the biological samples. Preliminary field results are also presented.
Release date: 2009-12-03 - Articles and reports: 11-522-X200800010976Description:
Many survey organizations use the response rate as an indicator for the quality of survey data. As a consequence, a variety of measures are implemented to reduce non-response or to maintain response at an acceptable level. However, the response rate is not necessarily a good indicator of non-response bias. A higher response rate does not imply smaller non-response bias. What matters is how the composition of the response differs from the composition of the sample as a whole. This paper describes the concept of R-indicators to assess potential differences between the sample and the response. Such indicators may facilitate analysis of survey response over time, between various fieldwork strategies or data collection modes. Some practical examples are given.
Release date: 2009-12-03 - Articles and reports: 11-522-X200800011000Description:
The present report reviews the results of a mailing experiment that took place within a large scale demonstration project. A postcard and stickers were sent to a random group of project participants in the period between a contact call and a survey. The researchers hypothesized that, because of the additional mailing (the treatment), the response rates to the upcoming survey would increase. There was, however, no difference between the response rates of the treatment group that received the additional mailing and the control group. In the specific circumstances of the mailing experiment, sending project participants a postcard and stickers as a reminder of the upcoming survey and of their participation in the pilot project was not an efficient way to increase response rates.
Release date: 2009-12-03 - Articles and reports: 82-003-X200900410933Geography: CanadaDescription:
This study examines the association between obesity and the relative percentages of fats, carbohydrates, protein and fibre in the diets of Canadians. The data are from the 2004 Canadian Community Health Survey - Nutrition.
Release date: 2009-10-21 - Articles and reports: 82-003-X200900310921Geography: CanadaDescription:
This study identifies, in a representative sample of Canadian children, age-related patterns of overweight and obesity between toddlerhood and childhood. The data are from cycles 2 through 5 (1996/1997 to 2002/2003) of the National Longitudinal Survey of Children and Youth. The sample comprised children aged 24 to 35 months at baseline, who were followed biennially over six years.
Release date: 2009-09-16 - Articles and reports: 11-536-X200900110803Description:
"Classical GREG estimator" is used here to refer to the generalized regression estimator extensively discussed for example in Särndal, Swensson and Wretman (1992). This paper summarize some recent extensions of the classical GREG estimator when applied to the estimation of totals for population subgroups or domains. GREG estimation was introduced for domain estimation in Särndal (1981, 1984), Hidiroglou and Särndal (1985) and Särndal and Hidiroglou (1989), and was developed further in Estevao, Hidiroglou and Särndal (1995). For the classical GREG estimator, fixed-effects linear model serves as the underlying working or assisting model, and aggregate-level auxiliary totals are incorporated in the estimation procedure. In some recent developments, an access to unit-level auxiliary data is assumed for GREG estimation for domains. Obviously, an access to micro-merged register and survey data involves much flexibility for domain estimation. This view has been adopted for GREG estimation for example in Lehtonen and Veijanen (1998), Lehtonen, Särndal and Veijanen (2003, 2005), and Lehtonen, Myrskylä, Särndal and Veijanen (2007). These extensions cover the cases of continuous and binary or polytomous response variables, use of generalized linear mixed models as assisting models, and unequal probability sampling designs. Relative merits and challenges of the various GREG estimators will be discussed.
Release date: 2009-08-11
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- Surveys and statistical programs – Documentation: 89-634-X2009008Geography: CanadaDescription:
The Strengths and Difficulties Questionnaire (SDQ) is a parent-reported instrument designed to provide information on children's behaviours and relationships. The SDQ consists of 25 items which are grouped into five subscales: (1) pro-social, (2) inattention-hyperactivity, (3) emotional symptoms, (4) conduct problems, and (5) peer problems. The SDQ was used to provide information on children aged 2 to 5 years in the 2006 Aboriginal Children's Survey (ACS). Though validated on general populations, the constructs of the SDQ have not been validated for off-reserve First Nations, Métis and Inuit children in Canada. The first objective of this evaluation is to examine if the five subscales of the SDQ demonstrate construct validity and reliability for off-reserve First Nations, Métis and Inuit children. The second objective is to examine if an alternative set of subscales, using the 25 SDQ items, may be more valid and reliable for off-reserve First Nations, Métis and Inuit children.
Release date: 2009-11-25