This paper investigated consequences of measurement error in the pretest on the estimate of the treatment effect in a pretest-posttest design with the analysis of covariance (ANCOVA) model, focusing on both the direction and magnitude of its bias. Some prior studies have examined the magnitude of the bias due to measurement error and suggested…

Pretest-posttest experimental designs are often used in randomized control trials (RCTs) in the education field to improve the precision of the estimated treatment effects. For logistic reasons, however, pretest data are often collected after random assignment, so that including them in the analysis could bias the posttest impact estimates. Thus,…

Growth is estimated most accurately by procedures involving the pretest-posttest difference, and for practical purposes all estimates involving this difference have approximately equal accuracy. In particular, the simple difference between pretest and posttest scores seems about as accurate as any other estimate, easier to compute, and meaningful…

An approach to teaching the mental status examination to sophomore medical students at the Wayne State University School of Medicine incorporates live simulations, a detailed handout, a pretest and post-test, and a short lecture and discussion. The data suggest significant post-test gains, but there were negative findings regarding the handout.…

The accuracy with which regression models estimate treatment effects is dependent upon a number of conditions. The stability of the regression line (a function of sample size and correlation between pretest and posttest) is said to be the most important of these conditions. The utility of regression models is proportional to the size of the…

Recent research results strongly suggest that the theoretical problems of change measures have limited practical significance for measuring individual growth, and it is important to determine whether this is also the case for measuring school impact. Accordingly, in this study artifical data were used to assess the correlation between several…

A computer simulation procedure was developed to reproduce the overall pattern of results obtained in the Educational Testing Service Growth Study. Then simulated data for seven sets of 10,000 to 15,000 cases were analyzed, and findings compared on the basis of correlations between estimated and true growth scores. Findings showed that growth was…

The four main approaches to measuring treatment effects in schools; raw gain, residual gain, covariance, and true scores; were compared. A simulation study showed true score analysis produced a large number of Type-I errors. When corrected for this error, this method showed the least power of the four. This outcome was clearly the result of the…