# standardized test scores

Many of the terms used in describing scores on standardized tests, such as stanine and percentile, are used in two senses. Statisticians use them to refer to points dividing the scores into groups, but counsellors often often use the words to describe the group rather than its boundaries, e.g., “Johnny is in the fifth stanine.”

Because scores on standardized tests depend on comparing an individual's score with the scores of a large group of test-takers, it is important to know what group is being used for the comparison.  For example, if Johnny scored in the fifth stanine, is that in relation to everyone who took the test in his school, in the community, in the state, or nationally? He might be in the ninth stanine locally and the fifth nationally.

In grading many standardized tests, the raw scores are normalized: points are added to or subtracted from the raw scores, according to the size of the score, until their distribution fits a symmetrical, bell-shaped curve.  For scores expressed in stanines, normalizing will put 4% of the testees in the first stanine, 7% in the second, and so on through 12%, 17%, 20%, 17%, 12%, 7%, and 4%. Having the scores fit a normal curve is very convenient for statistical purposes, but it assumes that whatever ability the test measures is evenly distributed around a central peak, which is questionable.