Pre/Post surveys and Post-program surveys assess how much participants have changed as a result of a program. Each has pros and cons that are important to consider as you decide which best fits your program measurement needs.
Pre/Post Surveys

What are they? A paired set of surveys to collect baseline data before the program, and then collect the same data on outcomes and experiences after the program. With the pre- and post-program data in hand, you can compare each survey respondent’s results before and after the program to assess how much they changed and how they experienced the program.

Pros: These surveys often measure change better over a long period of time, because participants are less able to ascertain and describe how they've changed. Additionally, they may work well with younger participants, who tend to struggle with the concept of looking back over time to assess how they’ve changed (as post-only surveys require).

Cons: This method requires a greater investment of resources, as two surveys must be developed and implemented. It requires that all participants respond to both surveys to analyze the data. Participants also may overestimate their understanding of a topic before the program, and as a result, the pre/post data may show that they haven’t changed, even if they have.

Furthermore, they tend to carry a risk of “social desiriability bias” (respondents tend to report socially acceptable attitudes and behaviors, and are less likely to report attitudes and behaviors that are less socially acceptable).

Post-program Surveys

What are they? Also called retrospective surveys, these tools ask participants to reflect and compare their knowledge and attitudes after the program is completed.

Pros: Post-program surveys are less time and resource intensive as there is only one survey to administer. This also means that your completion rate is likely to be higher, as participants only need to be present for one survey administration. Additionally, participants are less likely to have an inflated sense of how much they knew at the beginning and may be better able to characterize how much their knowledge and attitudes have changed.

Cons: This method may not be the right choice for long programs, or programs with very young participants. Post surveys also rely exclusively on participant perception and recall.

They tend to carry a higher risk of “courtesy bias” (participants tell you what they think you want to hear because they have received services from your program).