This is a simulation of how much students’ test scores in one classroom might vary, based on random factors that have no bearing on students’ mastery of subject matter. Imprecision is inherent in all tests of knowledge. Uncertain outcomes will always result. This spreadsheet model enables educators to trigger multiple test events, and note the degree to which a class of 26 students’ results will wander. (Audience: teachers, principals, instructional leaders) (Complexity: moderate)