s 38 - 40 will refer to the following scenario. Suppose Cabba manipulates both whether professors do or do not post their slides and whether professors do or do not require attendance, and Cabba measures class attednance as his DV. He finds that posting slides significantly reduces attendance when attendance is not required but does not affect attendance when attendance is required.Which of the following would be the most accurate description of Cabba's findings? There is an interaction effect, such that requring attendance improves class attendance, but only if slides are also posted. There are no main effects or interaction effects in Cabba's data. Both posting slides and requiring attendance have a main effect on class attendance, such that posting slides slides reduces attednace and requiring attendance improves attendence. There is an interaction effect, such that the effect of postings slides on attendance depends on whether the professor requires attendance. There is no main effect for either requiring attendance or posting slides