Sampling

How much data is enough?

Focus on what you need to make decisions

Assessment Cycle Image - Gather DataWhen considering how much evidence you should collect, consider the overall question that guides the inquiry, and how the results will be applied. If you are planning a programmatic overhaul, then you’ll probably want a larger sample with a lower error margin. However, the larger the sample, the greater the commitment of time required from faculty. A smaller sample is acceptable if the results will be used to inform minor curricular changes.

Your goal should be to gather a sample about which you will feel confident in using the results to inform program decisions. Suskie (2009) suggests: “collect enough evidence to feel reasonably confident that you have a representative sample of what your students have learned and can do” (p. 47).

  • “Simple” random samples are a straightforward way to obtain a representative sample as they give every student an equal chance of being selected.
  • Cluster random samples can be used with larger groups in the same fashion, by choosing a random sample of subgroups of students and collecting information from everyone in each subgroup.
  • Purposeful or judgment samples are “carefully, but not randomly chosen so that, in your judgment, they are representative of the students you are assessing” (Suskie, 2009, p. 49-50).

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