This page was rebuilt in 2026. The original video and text of this chapter were not preserved. The section "About this chapter" holds only facts recovered from the series; the section "Background" is a new, independent explanation of the topic, based on the sources listed at the end.
About this chapter
The Sampling Demonstration Series was a four-chapter video series on sampling for social norms campaigns, presented by Dr. Larry Hembroff and published on this site. Each chapter paired a video with exercises in SPSS. The final chapter, Sampling Demonstrations Part 4, covers non-response ("Non-Response is a Random Process") and is still available.
This was the second chapter of the series. Its exact topic was not preserved. The later chapters compare random samples with convenience samples, so this background section explains that difference.
Background: convenience samples and probability samples
A convenience sample includes whoever is easy to reach: students in one class, visitors to one event, volunteers who answer an open online link. A probability sample gives every member of the population a known, non-zero chance of selection, for example a simple random sample drawn from a full student list.
Convenience samples cost less and are fast, but the people who are easy to reach can differ systematically from everyone else, and there is no statistical basis for estimating how far the results are from the population values. Probability samples allow that estimate. For norms data, where the goal is to state what most members of a population actually do, this difference decides whether a message can be called accurate.
Sources
- Groves, R. M., Fowler, F. J., Couper, M. P., Lepkowski, J. M., Singer, E., & Tourangeau, R. (2009). Survey Methodology (2nd ed.). Hoboken, NJ: Wiley.
- Baker, R., Brick, J. M., Bates, N. A., Battaglia, M., Couper, M. P., Dever, J. A., Gile, K. J., & Tourangeau, R. (2013). Summary report of the AAPOR Task Force on Non-probability Sampling. Journal of Survey Statistics and Methodology, 1(2), 90-143.