Every test score contains an error of measurement. It is a misuse of any test score or any observation to accept it as a fixed, unchanging index containing no error. It does mean that the test score is being misused if knowledge of the size of the errors of measurement is not used in interpreting the score. In the case of most standardized test scores, the magnitude of the errors is made explicit, not hidden or unknown. In fact, the errors in essay grading or any other type of evaluative data have far larger but usually unknown errors of measurement.
Some people reject the notion of basing decisions on probabilistic data.
However, probability estimates are involved in almost all decisions. For example, the decision to cross a busy street at a particular instant is not made with a probability of 1.0 of doing so safely. For a test score represents only a sample from a limited domain and does not include the variety of factors that might influence that score. For example, in decisions determining admission to college, SAT scores should not be used in isolation and are in fact usually considered along with the pupil's high school record and other relevant data, such as teacher's or supervisor's recommendations concerning motivation, leadership ability, creativity, involvement in extracurricular activities, etc. All of these can then be evaluated against the student's socioeconomic background, along with consideration of any social obstacles or unusual physical demands required of the student to reach his current educational level.