A professor at a large university plans to conduct a study to compare the effect of online texts versus regular printed texts on student learning. If the findings are to be generalized to all students at the university, which of the following must be part of the design? a The students in the study should have experience using online and regular texts. b The students in the study should be a random sample from the population of students at the university. c The students should be allowed to choose which type of text they would like to use so that different learning styles are taken into consideration d The professor should collect data from all students in the population before generalizing results. e Only volunteer students should be used in the study because they are more likely to be active participants.