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- 1. International surveys: Motives and methodologies ArchivedArticles and reports: 12-001-X200800210754Description:
The context of the discussion is the increasing incidence of international surveys, of which one is the International Tobacco Control (ITC) Policy Evaluation Project, which began in 2002. The ITC country surveys are longitudinal, and their aim is to evaluate the effects of policy measures being introduced in various countries under the WHO Framework Convention on Tobacco Control. The challenges of organization, data collection and analysis in international surveys are reviewed and illustrated. Analysis is an increasingly important part of the motivation for large scale cross-cultural surveys. The fundamental challenge for analysis is to discern the real response (or lack of response) to policy change, separating it from the effects of data collection mode, differential non-response, external events, time-in-sample, culture, and language. Two problems relevant to statistical analysis are discussed. The first problem is the question of when and how to analyze pooled data from several countries, in order to strengthen conclusions which might be generally valid. While in some cases this seems to be straightforward, there are differing opinions on the extent to which pooling is possible and reasonable. It is suggested that for formal comparisons, random effects models are of conceptual use. The second problem is to find models of measurement across cultures and data collection modes which will enable calibration of continuous, binary and ordinal responses, and produce comparisons from which extraneous effects have been removed. It is noted that hierarchical models provide a natural way of relaxing requirements of model invariance across groups.
Release date: 2008-12-23 - Articles and reports: 12-001-X200800210755Description:
Dependent interviewing (DI) is used in many longitudinal surveys to "feed forward" data from one wave to the next. Though it is a promising technique which has been demonstrated to enhance data quality in certain respects, relatively little is known about how it is actually administered in the field. This research seeks to address this issue through behavior coding. Various styles of DI were employed in the English Longitudinal Study of Ageing (ELSA) in January, 2006, and recordings were made of pilot field interviews. These recordings were analysed to determine whether the questions (particularly the DI aspects) were administered appropriately and to explore the respondent's reaction to the fed-forward data. Of particular interest was whether respondents confirmed or challenged the previously-reported information, whether the prior wave data came into play when respondents were providing their current-wave answers, and how any discrepancies were negotiated by the interviewer and respondent. Also of interest was to examine the effectiveness of various styles of DI. For example, in some cases the prior wave data was brought forward and respondents were asked to explicitly confirm it; in other cases the previous data was read and respondents were asked if the situation was still the same. Results indicate varying levels of compliance in terms of initial question-reading, and suggest that some styles of DI may be more effective than others.
Release date: 2008-12-23 - Articles and reports: 12-001-X200800210756Description:
In longitudinal surveys nonresponse often occurs in a pattern that is not monotone. We consider estimation of time-dependent means under the assumption that the nonresponse mechanism is last-value-dependent. Since the last value itself may be missing when nonresponse is nonmonotone, the nonresponse mechanism under consideration is nonignorable. We propose an imputation method by first deriving some regression imputation models according to the nonresponse mechanism and then applying nonparametric regression imputation. We assume that the longitudinal data follow a Markov chain with finite second-order moments. No other assumption is imposed on the joint distribution of longitudinal data and their nonresponse indicators. A bootstrap method is applied for variance estimation. Some simulation results and an example concerning the Current Employment Survey are presented.
Release date: 2008-12-23 - 4. Variance estimation of changes in repeated surveys and its application to the Swiss survey of value added ArchivedArticles and reports: 12-001-X200800210758Description:
We propose a method for estimating the variance of estimators of changes over time, a method that takes account of all the components of these estimators: the sampling design, treatment of non-response, treatment of large companies, correlation of non-response from one wave to another, the effect of using a panel, robustification, and calibration using a ratio estimator. This method, which serves to determine the confidence intervals of changes over time, is then applied to the Swiss survey of value added.
Release date: 2008-12-23 - Articles and reports: 82-003-X200800310681Geography: CanadaDescription:
This article describes the methods used to link census data from the long-form questionnaire to mortality data, and reports simple findings for the major groups, defined by income, education, occupation, language and ethnicity, Aboriginal or visible minority status, and disability status.
Release date: 2008-09-17 - 6. Measuring health in population surveys ArchivedArticles and reports: 11-522-X200600110370Description:
Many countries conduct surveys that focus specifically on their population's health. Because health plays a key role in most aspects of life, health data are also often collected in population surveys on other topics. The subject matter of population health surveys broadly encompasses physical and mental heath, dental health, disabilities, substance abuse, health risk factors, nutrition, health promotion, health care utilization and quality, health coverage, and costs. Some surveys focus on specific health conditions, whereas others aim to obtain an overall health assessment. Health is often an important component in longitudinal studies, particularly in birth and aging cohorts. Information about health can be collected by respondents' reports (for themselves and sometimes for others), by medical examinations, and by collecting biological measures. There is a serious concern about the accuracy of health information collected by respondents' reports. Logistical issues, cost considerations, and respondent cooperation feature prominently when the information is collected by medical examinations. Ethical and privacy issues are often important, particularly when DNA and biomarkers are involved. International comparability of health measures is of growing importance. This paper reviews the methodology for a range of health surveys and will discuss the challenges in obtaining accurate data in this field.
Release date: 2008-03-17 - Articles and reports: 11-522-X200600110398Description:
The study of longitudinal data is vital in terms of accurately observing changes in responses of interest for individuals, communities, and larger populations over time. Linear mixed effects models (for continuous responses observed over time) and generalized linear mixed effects models and generalized estimating equations (for more general responses such as binary or count data observed over time) are the most popular techniques used for analyzing longitudinal data from health studies, though, as with all modeling techniques, these approaches have limitations, partly due to their underlying assumptions. In this review paper, we will discuss some advances, including curve-based techniques, which make modeling longitudinal data more flexible. Three examples will be presented from the health literature utilizing these more flexible procedures, with the goal of demonstrating that some otherwise difficult questions can be reasonably answered when analyzing complex longitudinal data in population health studies.
Release date: 2008-03-17 - Articles and reports: 11-522-X200600110444Geography: Province or territoryDescription:
General population health surveys often include small samples of smokers. Few longitudinal studies specific to smoking have been carried out. We discuss development of the Ontario Tobacco Survey (OTS) which combines a rolling longitudinal, and repeated cross-sectional components. The OTS began in July 2005 using random selection and data-collection by telephones. Every 6 months, new samples of smokers and non-smokers provide data on smoking behaviours and attitudes. Smokers enter a panel study and are followed for changes in smoking influences and behaviour. The design is proving to be cost effective in meeting sample requirements for multiple research objectives.
Release date: 2008-03-17 - Articles and reports: 75F0002M1992003Description:
As SLID is a longitudinal survey, it is desirable to retain respondents in the sample for as long as possible. However, sample attrition and changes in the popu lation result in the sample becoming less representative of the population as time passes. To balance these factors, the sample for a longitudinal survey may be comprised of panels, with each panel being representative of the target population. Starting with a fixed sample size, the paper examines feasible options for the number of panels in the sample and the length of time which each panel remains in the survey. The rationale for the selected option is reviewed.
Release date: 2008-02-29 - Articles and reports: 75F0002M1992005Description:
In recent years a considerable amount of attention has been focused on what is known as the "seam" problem in surveys having a longitudinal design. This refers to the fact that the number of transitions or changes in status observed across the seam when the data for two consecutive reference periods are juxtaposed is considerably larger (so metimes, an order of magnitude larger) than the average number observed in the data reported for a single reference period.
Response errors are the most probable cause of seam biases. For characteristics such as employment status or income recipiency, errors can be due to omissions or to misplacing events in time. However, standard explanations for response errors based on "forgetting theory" are not supported by the data. Results concerning proxy effects are mixed but generally show no clear association.
Dependent interviewing (i.e., feeding back to respondents responses provided on a previous interview) would appear the most appropriate strategy for dealing with seam effects. However, not all feedback techniques will necessarily work. A comparison of two such techniques, one which failed to eliminate seam effects (SIPP) and one which was successful (LMAS) and which has also been successfully tested by SIPP, attempts to identify the key features required.
The paper argues in closing that dependent interviewing should not be viewed as a necessary evil that is required for reducing seam biases but as an integral part of the interview process in longitudinal surveys.
Release date: 2008-02-29
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- 1. International surveys: Motives and methodologies ArchivedArticles and reports: 12-001-X200800210754Description:
The context of the discussion is the increasing incidence of international surveys, of which one is the International Tobacco Control (ITC) Policy Evaluation Project, which began in 2002. The ITC country surveys are longitudinal, and their aim is to evaluate the effects of policy measures being introduced in various countries under the WHO Framework Convention on Tobacco Control. The challenges of organization, data collection and analysis in international surveys are reviewed and illustrated. Analysis is an increasingly important part of the motivation for large scale cross-cultural surveys. The fundamental challenge for analysis is to discern the real response (or lack of response) to policy change, separating it from the effects of data collection mode, differential non-response, external events, time-in-sample, culture, and language. Two problems relevant to statistical analysis are discussed. The first problem is the question of when and how to analyze pooled data from several countries, in order to strengthen conclusions which might be generally valid. While in some cases this seems to be straightforward, there are differing opinions on the extent to which pooling is possible and reasonable. It is suggested that for formal comparisons, random effects models are of conceptual use. The second problem is to find models of measurement across cultures and data collection modes which will enable calibration of continuous, binary and ordinal responses, and produce comparisons from which extraneous effects have been removed. It is noted that hierarchical models provide a natural way of relaxing requirements of model invariance across groups.
Release date: 2008-12-23 - Articles and reports: 12-001-X200800210755Description:
Dependent interviewing (DI) is used in many longitudinal surveys to "feed forward" data from one wave to the next. Though it is a promising technique which has been demonstrated to enhance data quality in certain respects, relatively little is known about how it is actually administered in the field. This research seeks to address this issue through behavior coding. Various styles of DI were employed in the English Longitudinal Study of Ageing (ELSA) in January, 2006, and recordings were made of pilot field interviews. These recordings were analysed to determine whether the questions (particularly the DI aspects) were administered appropriately and to explore the respondent's reaction to the fed-forward data. Of particular interest was whether respondents confirmed or challenged the previously-reported information, whether the prior wave data came into play when respondents were providing their current-wave answers, and how any discrepancies were negotiated by the interviewer and respondent. Also of interest was to examine the effectiveness of various styles of DI. For example, in some cases the prior wave data was brought forward and respondents were asked to explicitly confirm it; in other cases the previous data was read and respondents were asked if the situation was still the same. Results indicate varying levels of compliance in terms of initial question-reading, and suggest that some styles of DI may be more effective than others.
Release date: 2008-12-23 - Articles and reports: 12-001-X200800210756Description:
In longitudinal surveys nonresponse often occurs in a pattern that is not monotone. We consider estimation of time-dependent means under the assumption that the nonresponse mechanism is last-value-dependent. Since the last value itself may be missing when nonresponse is nonmonotone, the nonresponse mechanism under consideration is nonignorable. We propose an imputation method by first deriving some regression imputation models according to the nonresponse mechanism and then applying nonparametric regression imputation. We assume that the longitudinal data follow a Markov chain with finite second-order moments. No other assumption is imposed on the joint distribution of longitudinal data and their nonresponse indicators. A bootstrap method is applied for variance estimation. Some simulation results and an example concerning the Current Employment Survey are presented.
Release date: 2008-12-23 - 4. Variance estimation of changes in repeated surveys and its application to the Swiss survey of value added ArchivedArticles and reports: 12-001-X200800210758Description:
We propose a method for estimating the variance of estimators of changes over time, a method that takes account of all the components of these estimators: the sampling design, treatment of non-response, treatment of large companies, correlation of non-response from one wave to another, the effect of using a panel, robustification, and calibration using a ratio estimator. This method, which serves to determine the confidence intervals of changes over time, is then applied to the Swiss survey of value added.
Release date: 2008-12-23 - Articles and reports: 82-003-X200800310681Geography: CanadaDescription:
This article describes the methods used to link census data from the long-form questionnaire to mortality data, and reports simple findings for the major groups, defined by income, education, occupation, language and ethnicity, Aboriginal or visible minority status, and disability status.
Release date: 2008-09-17 - 6. Measuring health in population surveys ArchivedArticles and reports: 11-522-X200600110370Description:
Many countries conduct surveys that focus specifically on their population's health. Because health plays a key role in most aspects of life, health data are also often collected in population surveys on other topics. The subject matter of population health surveys broadly encompasses physical and mental heath, dental health, disabilities, substance abuse, health risk factors, nutrition, health promotion, health care utilization and quality, health coverage, and costs. Some surveys focus on specific health conditions, whereas others aim to obtain an overall health assessment. Health is often an important component in longitudinal studies, particularly in birth and aging cohorts. Information about health can be collected by respondents' reports (for themselves and sometimes for others), by medical examinations, and by collecting biological measures. There is a serious concern about the accuracy of health information collected by respondents' reports. Logistical issues, cost considerations, and respondent cooperation feature prominently when the information is collected by medical examinations. Ethical and privacy issues are often important, particularly when DNA and biomarkers are involved. International comparability of health measures is of growing importance. This paper reviews the methodology for a range of health surveys and will discuss the challenges in obtaining accurate data in this field.
Release date: 2008-03-17 - Articles and reports: 11-522-X200600110398Description:
The study of longitudinal data is vital in terms of accurately observing changes in responses of interest for individuals, communities, and larger populations over time. Linear mixed effects models (for continuous responses observed over time) and generalized linear mixed effects models and generalized estimating equations (for more general responses such as binary or count data observed over time) are the most popular techniques used for analyzing longitudinal data from health studies, though, as with all modeling techniques, these approaches have limitations, partly due to their underlying assumptions. In this review paper, we will discuss some advances, including curve-based techniques, which make modeling longitudinal data more flexible. Three examples will be presented from the health literature utilizing these more flexible procedures, with the goal of demonstrating that some otherwise difficult questions can be reasonably answered when analyzing complex longitudinal data in population health studies.
Release date: 2008-03-17 - Articles and reports: 11-522-X200600110444Geography: Province or territoryDescription:
General population health surveys often include small samples of smokers. Few longitudinal studies specific to smoking have been carried out. We discuss development of the Ontario Tobacco Survey (OTS) which combines a rolling longitudinal, and repeated cross-sectional components. The OTS began in July 2005 using random selection and data-collection by telephones. Every 6 months, new samples of smokers and non-smokers provide data on smoking behaviours and attitudes. Smokers enter a panel study and are followed for changes in smoking influences and behaviour. The design is proving to be cost effective in meeting sample requirements for multiple research objectives.
Release date: 2008-03-17 - Articles and reports: 75F0002M1992003Description:
As SLID is a longitudinal survey, it is desirable to retain respondents in the sample for as long as possible. However, sample attrition and changes in the popu lation result in the sample becoming less representative of the population as time passes. To balance these factors, the sample for a longitudinal survey may be comprised of panels, with each panel being representative of the target population. Starting with a fixed sample size, the paper examines feasible options for the number of panels in the sample and the length of time which each panel remains in the survey. The rationale for the selected option is reviewed.
Release date: 2008-02-29 - Articles and reports: 75F0002M1992005Description:
In recent years a considerable amount of attention has been focused on what is known as the "seam" problem in surveys having a longitudinal design. This refers to the fact that the number of transitions or changes in status observed across the seam when the data for two consecutive reference periods are juxtaposed is considerably larger (so metimes, an order of magnitude larger) than the average number observed in the data reported for a single reference period.
Response errors are the most probable cause of seam biases. For characteristics such as employment status or income recipiency, errors can be due to omissions or to misplacing events in time. However, standard explanations for response errors based on "forgetting theory" are not supported by the data. Results concerning proxy effects are mixed but generally show no clear association.
Dependent interviewing (i.e., feeding back to respondents responses provided on a previous interview) would appear the most appropriate strategy for dealing with seam effects. However, not all feedback techniques will necessarily work. A comparison of two such techniques, one which failed to eliminate seam effects (SIPP) and one which was successful (LMAS) and which has also been successfully tested by SIPP, attempts to identify the key features required.
The paper argues in closing that dependent interviewing should not be viewed as a necessary evil that is required for reducing seam biases but as an integral part of the interview process in longitudinal surveys.
Release date: 2008-02-29
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