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GEM 2004 Stephen Hunt Adult Population Survey Sampling

GEM 2004 Stephen Hunt Adult Population Survey Sampling. GEM Survey Sampling: Current Situation. GEM Global: uses a variety of sampling methods, and procedures. · Telephone / face to face interviews · Quota and random sampling.

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GEM 2004 Stephen Hunt Adult Population Survey Sampling

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  1. GEM 2004Stephen HuntAdult Population Survey Sampling

  2. GEM Survey Sampling: Current Situation GEM Global: uses a variety of sampling methods, and procedures. ·Telephone / face to face interviews ·Quota and random sampling. This reflects the ad hoc nature of the project’s development. These methods are, often, effectively imposed on the project by the survey firms, due to the fact that very few methodological demands are placed on the survey firms.

  3. GEM Survey Sampling: Current Situation The current survey sampling ‘methodology’ or data gathering procedures GEM uses 1.Lacks scientific, rather than pragmatic, justification. 2.Poorly documented, e.g. non-responses not universally recorded. 3.Offers little guidance concerning data gathering to new teams, especially those in the developing world. In sum: GEM’s APS data gathering activities lack uniformity & normative standards

  4. GEM Survey Sampling: Current Situation This conclusion is important because ·GEM is always open to on going critical comment/ analysis/ estimation of its methodology, as well as its output etc.. ·This process will almost certainly take place should any bid for funding be made to institutions like the EU.  Such Peer Review will probably be conducted by people involved in the European Social Survey: & this will almost certainly be taken as the standard against which survey based research is judged.

  5. GEM Survey Sampling: Suggestions In order to enhance the methodological basis on which GEM is founded & increase the likelihood of positive Peer Review: Recommendations 1. Sampling Method:Develop a standardised sampling methodology 2. Survey Template: Develop a set of descriptive items completion of which documents the proposed survey so it’s adequacy can be assessed & if completed allows statistical features of the sample to be computed after the survey. 3. Survey firms:Progressive move from ‘market research’ firms to University based or affiliated survey agencies.

  6. GEM Survey Sampling: Sampling Method Quota sampling – Completing quotas - usually in terms of certain demographics such as sex or age band - of desired numbers of respondents (sample cases) proportional to their population frequencies. Hence arriving at an approximation of a representative sample of the population BUT ONLY in terms of the specified quotas. But this is non-scientific method of gathering respondents. Open to interviewer bias – only selecting the most accessible respondent, any respondent difficult to contact is ignored and so potentially the sample can be unrepresentative except in terms of the designated quotas. As a quota sample has unknown statistical properties such bias & unrepresntativeness are impossible to detect – except by comparing the results to a random sample

  7. GEM Survey Sampling: Sampling Method Random sampling A sample attains randomisation via application of a chance mechanism as the procedure of respondent selection from a frame. A representative sample is arrived at by default. Essentially, the interviewer keeps going back to a randomly designated respondent until they answer Certain constraints can be built into the sample procedure, such as stratification & clustering, to minimise any bias & ensure over sampling where required. Such a sample can have its statistical properties calculated. However, even random samples can fail to deliver an entirely representative sample if the total number of respondents is small, or even just by chance. This potential is addressed by weighting the sample.

  8. Standardised Survey Template: Completed before the Survey

  9. Standardised Survey Template: Computing Statistical Properties A Simple Random Sample has transparent ‘statistical properties’. Any deviation from Simple Random Sample means the statistical properties can no longer be determined as if the sample were randomly selected, e.g. Also the impact of the deviation has to be calculated e.g. mean, standard error, etc

  10. Standardised Survey Template: Computing Statistical Properties • Effective sample size (neff) • Design Effect (DEFF) • Design Factor (DEFT) • These features of the sample impact on the • Standard Error • Confidence Intervals

  11. GEM Survey Sampling: Sampling Method Additional Costs Random Surveys are more expensive The additional cost for a randomised survey as opposed to a quota sample in Finland is about 25%

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