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…

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…