PSYC 3250 Lecture Notes - Percentile Rank, Linear Map, Percentile
10 Oct 2012
School
Department
Course
Professor
Document Summary
Raw scores, which represent simple counts of the behaviours sampled by the test or measuring procedure, do not always provide useful information. It is often necessary to re-express, or transform, raw scores into some more informative scale. Scale - the set of scores that might be reported for a test. Scales are very often transformations of the original raw scores. The simplest transformation is one that expresses scores in terms of percentage rather than raw units. Transformed score = constant + (weight x raw score) This form of a transformation guarantees a simple, direct relationship between raw scores and transformed scores that can be depicted using a straight line. The z transformation is extremely useful for a number of reasons. Rst, the z score indicates each person s standing as compared with the group mean. When the distribution of raw scores is reasonably normal, z scores can be directly converted to percentiles.
