In my last post, I talked about the difference between program evaluation and student assessment. I also touched on using existing assessments if they are available and appropriate, and if not, constructing new assessments. Of course, that new assessment would need to meet test quality standards or otherwise it will not be able to measure what you need to have measured for your evaluation. Test quality has to do with validity and reliability.
When a test is valid, it means that when a student responds with a wrong answer, it would be reasonable to conclude that they did so because they did not learn what they were supposed to have learned. There are all kinds of impediments to an assessment’s validity. For example, if in a science class you are asking students a question aimed at determining if they understand the difference between igneous and sedimentary rocks, yet you know that some of them do not understand English, you wouldn’t want to ask them the question in English. In testing jargon, what you are introducing in such a situation is “construct irrelevant variance.” In this case, the variance in results may be as much due to whether they know English (the construct irrelevant part) as to whether they know the construct, which is the differences between the rock types. Hence, these results would not help you determine if your innovation is helping them learn the science better.
Reliability has to do with test design, administration, and scoring. Examples of unreliable tests are those that are too long, introducing test-taking fatigue that interfere with their being reliable measures of student learning. Another common example of unreliability is when the scoring directions or rubric are not designed well enough to be sufficiently clear about how to judge the quality of an answer. This type of problem will often result in inconsistent scoring, otherwise known as low interrater reliability.
To summarize, a student learning assessment can be very important to your evaluation if a goal of your project is to directly impact student learning. Then you have to make some decisions about whether you can use existing assessments or develop new ones, and if you make new ones, they need to meet technical quality standards of validity and reliability. For projects not directly aiming at improving student learning, an assessment may actually be inappropriate in the evaluation because the tie between the project activities and the student learning may be too loose. In other words, the learning outcomes may be mediated by other factors that are too far beyond your control to render the learning outcomes useful for the evaluation.