Reliability And Statistical Methods' Selection Of Pretest-posttest Design Data

Pretest-posttest designs are widely used in psychology and medicine. Its main use is the questionary in psychology. In some time interval, the same subjects were repeatedly investigated on the same questionary. The difference between two measurements is the time of measurements. Because any intervention hasn't been applied, test-retest reliability can be estimated through correlation analysis of pretest and posttest scores. In scientific research of medicine, the most of pretest-posttest designs aren't different from the questionaries in psychology. The purpose of medical studies is mainly to inspect the effect of treatment, so the posttest is usually measured after imposition of the treatment intervention and the condition of two measurements isn't identical. It need to study that How to compute test-retest reliability. The reliability of difference scores is a confusing question. The first goal of my topic is to explore reliability of pretest-posttest designs and difference scores.