Question

You believe that requiring students to attend a series of presentations on study skills will improve their grades. You are concerned that boys and girls might react differently to such a series, and that students in grades 9 and 10 might react differently than those in grades 11 and 12. You set up an experiment involving 100 students in ninth and tenth grade and 100 students in eleventh and twelfth grade. (Assume there are equal numbers of girls and boys in each grade.) You intend to measure improvement based on pre- and post-treatment grade-point averages.