There are different types of plans that guide an evaluation exercise. I define three of them in this post.
Terms of reference (ToR)… Stakeholder expectations to be met by the evaluator, and evaluator expectations to be met by the client. The document is like a contract.
Evaluation design… The purpose and objectives of the evaluation exercise, and the means for achieving them. The primary function of the design is to anticipate possible alternative explanations for program results, and describe data collection and analysis methods to render implausible as many of them as feasible, leaving a stronger case that results can be attributed to program implementation.
Evaluation plan… Day-by-day assignments for each member of the evaluation team for each day of the exercise.