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EMR 6500: Survey Research

EMR 6500: Survey Research. Dr. Chris L. S. Coryn Spring 2012. Agenda. Stratified random sampling for means and totals Review. Stratified Random Sampling. Stratified Random Sampling.

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EMR 6500: Survey Research

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  1. EMR 6500:Survey Research Dr. Chris L. S. Coryn Spring 2012

  2. Agenda Stratified random sampling for means and totals Review

  3. Stratified Random Sampling

  4. Stratified Random Sampling Astratified random sample is one in which some form of random sampling is applied in each of a set of separate groups formed from all entries on a sampling frame from which a sample is to be drawn

  5. Strata In stratified random sampling, strata are nonoverlapping groups separating population elements By strategically forming these groups, stratification becomes a feature of the sample design that can improve the statistical quality of survey estimates

  6. Notation for Stratified Random Sampling

  7. Allocation to Strata Deciding how a stratified sample will be distributed among all strata is called stratum allocation The most appropriate allocation method depends on how the stratification will be used

  8. Equal Allocation If the main purpose of stratification is to control subgroup sample sizes for important population subgroups, stratum sample sizes should be sufficient to meet precision requirements for subgroup analysis An important part of the analysis is to produce comparisons among all subgroup strata In this instance, equal allocation (i.e., equal sample sizes) would be appropriate

  9. Proportionate Allocation Proportionate allocation is a prudent choice when the main focus of the analysis is characteristics of several subgroups or the population as a whole and where the appropriate allocations for these analyses are discrepant Proportionate allocation involves applying the same sampling rate to all strata, thus implying that the percent distribution of the selected sample among strata is identical to the corresponding distribution for the population

  10. Optimum Allocation Optimum allocation, in which the most cost-efficient stratum sample sizes are sought, can lead to estimates of overall population characteristics that are statistically superior to those from proportionate allocations When all stratum unit costs are the same, the stratum sampling rates that yield the most precise sample estimates are proportional to the stratum-specific standard deviations (Neyman allocation)

  11. Estimation of a Population Mean and Total

  12. Estimate of Population Mean

  13. Example for a Population Mean

  14. Example for a Population Mean

  15. Estimate of Population Total

  16. Example for Population Total

  17. Selecting the Sample Size for Estimating Population Means and Totals

  18. Sample Size for Estimating Population Means and Totals

  19. Example for a Population Mean

  20. Example for a Population Mean

  21. Example for a Population Mean

  22. Example for a Population Mean

  23. Neyman Allocation

  24. Neyman Allocation

  25. Neyman Allocation

  26. Neyman Allocation

  27. Neyman Allocation

  28. Proportionate Allocation

  29. Proportionate Allocation

  30. Proportionate Allocation

  31. Proportionate Allocation

  32. Comparison of Allocation Methods Proportionate Neyman General framework

  33. Review

  34. The Tailored Design Method

  35. The Tailored Design Method Uses multiple motivational features in compatible and mutually supportive ways to encourage high quantity and quality of responses

  36. The Tailored Design Method Premised on social exchange perspective on human behavior Assumes that the likelihood of responding is greater when the expected rewards outweigh the anticipated costs

  37. The Tailored Design Method Gives attention to all aspects of contacting and communicating with respondents Encourages response by considering survey sponsorship, the nature of the population and variations within it, and content of questions

  38. The Tailored Design Method Emphasizes reducing errors of coverage, sampling, nonresponse, and measurement

  39. Coverage Error Occurs when all members of a population do not have a known, non-zero probability of selection Occurs when those who are excluded are different from those who are included

  40. Sampling Error Results from surveying only some rather than all members of a population Represented by B, the bound on the error of estimation

  41. Nonresponse Error • Occurs when people selected do not respond and are different than those who do • Nonresponse can occur at the level of items within a survey or at the level of the survey • MAR • MCAR

  42. Measurement Error Occurs when responses are inaccurate or imprecise Primarily related to poor layout and poor design and wording of questions

  43. Social Exchange and Surveys • Addresses three central questions about design and implementation • How can the perceived rewards for responding be increased? • How can the perceived costs of responding be reduced? • How can trust be established so that people believe the rewards will outweigh the costs of responding?

  44. Increasing Benefits Provide information about the survey Ask for help or advise Show positive regard Say thank you Support group values Give tangible rewards Make the questionnaire interesting Provide social validation Inform people that opportunities to respond are limited

  45. Decreasing Costs Make it convenient to respond Avoid subordinating language Make the questionnaire short and easy to complete Minimize requests for personal or sensitive information Emphasize similarity to other requests or tasks to which a person has already responded

  46. Establishing Trust Obtain sponsorship by legitimate authority Provide a token of appreciation in advance Make the task appear important Ensure confidentiality and security of information

  47. Features that can be Tailored • Survey mode • Singular or multiple • Sample design • Type of sample • Number of units sampled • Incentives • Type of incentive • Amount or cost of incentive • Before or after

  48. Features that can be Tailored • Contacts • Number of contacts • Timing of initial and subsequent contacts • Mode of each contact • Whether contacts will be personalized • Sponsorship information • Visual design of each contact • Text or words in each contact

  49. Features that can be Tailored • Additional materials • Whether to provide them at all • Type of materials (e.g., research report) • Visual design of materials • Text or wording of materials

  50. Features that can be Tailored • Questionnaire • Topics included • Length (duration, number of pages/screens, number of questions) • First page or screen • Visual design • Organization and order of questions • Navigation through questionnaire

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