Interpreting Test Scores
As a measurement tool, a test results in a score—a number. A number, however, has no intrinsic meaning and must be compared with something that has meaning in order to interpret it. For a test score to be useful for making decisions about the test, the score has to be interpreted by the teacher. Whether the interpretations are norm- or criterion-referenced, a basic knowledge of statistical concepts is necessary to assess the quality of teacher-made or published tests, understand standardized test scores, summarize assessment results, and explain test scores to others.
Some information about how a test performed as a measurement instrument can be obtained from computer-generated test- and item-analysis reports. In addition to providing item analysis data such as difficulty and discrimination indexes, such reports often summarize the characteristics of the score distribution. If the teacher does not have access to machine scoring and computer software for test and item analysis, many of these analyses can be done by hand, albeit more slowly.
When a test is scored, the teacher is left with a collection of raw scores. Often these scores are recorded according to the names of the students, in alphabetical order, or by student numbers. As an example, suppose that the scores displayed in Table 15.1 resulted from the administration of a 65-point test to 16 nursing students.
Glancing at this collection of numbers, the teacher would find it difficult to answer such questions as: