Dr. richards is interested in conducting a psychological study with his class? he is interested in how much influence being in a fraternity or sorority has on his students' performance in class. he offers the students the opportunity to be in the study in exchange for extra credit points. any students who did not want to participate in the study were offered another option to earn the extra credit points. 148 students decide to participate in the study. dr. richards has each participant fill out a questionnaire asking them a variety of questions, including the question "are you a member or a sorority or fraternity? " once dr. richards collects and analyzes the data, he finds that students who are members of a sorority or fraternity do not perform as well in class as those who are not members of a sorority or fraternity. dr. richards is conducting a(n) study.