Data collected from the interview can be difficult to analyze, quantify, and aggregate. Tests of Knowledge. It is even possible to have the respondent demonstrate specific procedures as a form of test. If questions are carefully selected to demonstrate the student's mastery of a particular knowledge base or skill-set, tests have the advantage of assuring the evaluator that the respondent either has or has not acquired a set of knowledge. Tests of knowledge can be costly and time-consuming to prepare.
Many respondents find such tests to be threatening and aversive.
There are also limits to how much one can infer from the results of a written test about the respondent's actual behavior. For example, a test that assesses a teacher's awareness of specific teaching practices will indicate the instructor's knowledge but does not provide insight into their classroom practices. In direct observation, a recorder observes and records behavior of interest to the program evaluator. The observer takes running anecdotal notes of the behavior being observed. These notes may be unstructured, with the recorder relying on his or her subjective viewpoint in determining which behaviors or occurrences to record and which to omit.