Psychometrics of Quality of Life Measurement General Background The quality of a test is judged by three major standards: (1) validity, (2) reliability, and (3) practicality. Validity reflects how well a test measures what it is intended to measure. For example, a test of reading comprehension could lose validity if it allows too little time for taking the test. It might actually measure reading speed rather than comprehension. Reliability refers to the consistency of results achieved by the test. To establish reliability, a test may be given to the same group several times. If very similar results are obtained each time, the test may be considered highly reliable. Practicality involves the cost and convenience of the test. If a test requires too much expense or effort, it may be impractical. It also may be impractical if the results are too difficult to interpret.
(Excerpted from the World Book, author James Crouse, Ph.D., Professor of Education and Sociology, University of Delaware.)
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