Session 4: Sampling and Data Collection. Objectives for Session 4: Finish in-class data activity – delivery of services in ten food pantries Sampling.
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Presentation on theme: "Session 4: Sampling and Data Collection. Objectives for Session 4: Finish in-class data activity – delivery of services in ten food pantries Sampling."— Presentation transcript:
Objectives for Session 4: Finish in-class data activity – delivery of services in ten food pantries Sampling in evaluation designs Consider a formative design for the New Jersey Division of Youth and Family Services
Sampling and External Validity To whom do we wish to generalize? From what population were the cases selected? How were cases selected? Are these cases representative of the population from which they were selected?
Probability Sampling Random Sampling Stratified Random Sampling –Randomly selecting within certain characteristics, sort into strata or groups Cluster Sampling –Randomly select through a hierarchy (typically geographic) to get down to unit of analysis
Nonprobability Sampling Non-random selection –Purposive, Snowball Environmental or contextual factors external to the program Vary your cases on the key dimensions of interest Gather data from individuals or sources that are credible
Issues to Bear in Mind Selection bias Meaning of non-response Challenges of implementing a sampling strategy –gaining access –confidentiality –documentation, verification, data cleaning
New Jersey Division of Youth and Family Services Utility of a formative evaluation? What might we focus upon? Valid measures of service delivery? Potential sources of data? –Primary and secondary data sources? Sampling strategy?
Readings and Assignment for Next Time: Morgan, pp. 7-45 “Focus Groups for Social and Market Research” Chetkovich et al. “Informed Policy Making For The Prevention Of Unwanted Pregnancy.” Conducting Focus Groups in class on Wed. –Turn in guides at the beginning of class –Be on time, we will begin class right at the top of the hour !!!