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 first chapter of the series. Its exact topic was not preserved.
Background: populations and samples
A social norms campaign rests on data about a defined group: the students of one campus, the residents of one county, the members of one team. That whole group is the population. Asking every member is rarely possible, so most projects survey a sample, a subset of the population, and use it to estimate the population's real behaviors and its perceptions of peers.
How well a sample stands for its population depends far more on how the sample is chosen than on how large it is. A large sample drawn in a biased way can still give wrong estimates, while a well-drawn random sample of modest size can estimate population values within a known margin of error.
For a norms campaign this matters twice: the campaign's message ("most students…") must come from data that represent the population, and later evaluation must compare like with like across survey waves.
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.