Unlike the student's Grade Point Average, which is made up of grades assigned by a variety of teachers with a variety of standards, personal subjectivity has been eliminated in the scoring of objective tests. With closed questions there is only one right answer, and those who mark that answer get a point. Essay portions of standardized tests are evaluated using rigorous criteria, and raters are checked to assure that they are following the criteria. Thus, even the evaluation of open-ended responses includes a minimum of subjectivity.
Before being administered to "real" populations, standardized tests are pilot-tested with other groups, and the results are statistically analyzed to assure that the test has a high reliability. Reliability refers to the likelihood that if the same person took the test more than once, it is extremely likely that the scores on the different testings would be close to identical. Assuming the person's knowledge is approximately the same day to day, this is the result the tester hopes to get. If the person's scores fluctuated widely, it would be reasonable to suspect that the fluctuating scores are due to something about the test, such as unclear questions that result in a high level of guessing.
Validity refers to the degree to which scores on a test reflect what the test is supposed to measure. On a valid social studies test, those who know more social studies should get higher scores than those who know less. However, if a test maker is not careful and uses sophisticated vocabulary, test scores might be contaminated by student vocabulary level. Students who know a lot of social studies content might get lower scores because they don't understand the questions being asked due to their weaker vocabularies. Problems like this regularly contaminate the validity of classroom tests constructed by teachers who aren't aware of the subtleties of standardized-test construction.
Dr. Art Bangert, Professor of Education at the University of Montana, points out that standardized tests are better than other indicators of a student's preparedness for doing college-level work. Standardized tests help make comparisons of students with widely different high school experiences. Standardized tests, because all are held to the same standards, are also helpful for comparing achievement of students in different school districts, states, or parts of the country,