“…Another interpretation, of course, is simply that the pretest was ineffective in influencing the effect of the experimental treatment. Of 14 other studies of attitude change (Berrien, 1950;Cromwell, 1955;Green, 1952;Jarrett & Sherriffs, 1953;Kelley & Volhkert, 293 1952;Kelman, 1953;Lindgren, 1944;Maas, 1950;Osgood & Tannenbaum, 1955;Plant, 1956;Sawyer, 1954;Thistlethwaite & Kamenetzky, 1955;Wagman, 1955;Weiss, 1953) which utilized a pretest-treatment-posttest design, all failed to control for the possibility of the interaction effect described above.…”