## How much data is enough?

## Focus on what you **need** to make decisions

When 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.

“Collect enough evidence to feel reasonably confident that you have a representative sample of what your students have learned and can do” (Suskie, 2009, 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).