You may have heard the old adage, "Stay with your first answer on a multiple-choice test." Is changing answers more likely to be helpful or harmful? To examine this, Best (1979) studied the responses of 261 students in an introductory psychology course. He recorded the number of right-to-wrong, wrong-toright, and wrong-to-wrong answer changes for each student. More wrong-to-right changes than right-to-wrong changes were made by 195 of the students, who were thus "helped" by changing answers; 27 students made more right-to-wrong changes than wrong-to-right changes and thus "hurt" themselves.
(a) For these 222 students, conduct a X2 test of the hypothesis that the population proportions of right-to-wrong and wrong-to-right changes are equal. Your conclusions?
(b) What is the effect size?