The measurement of change is fundamental in the social and behavioral sciences. Many researchers have used change scores to measure gain in ability or shift in attitude over time, or difference scores between two variables to measure a construct (e.g., self-concept vs. ideal self). This entry introduces estimation of change scores, its assumptions and applications, and at the end offers a recommendation on the use of change scores.
Let Y and X stand for the measures obtained by applying the same test to the subjects on two occasions. Observed change or difference score is D = Y–X. The true change is DT = YT–XT, where YT and XT represent the subject's true status [Page 143]at these times. The development of measuring the true change DT follows ...
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