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…