Mary and Gary are both doing research on the effects of sleep deprivation on critical thinking. Mary recruited 20 students. Believing that grade point average (GPA) may be a confounding variable, she...

Extracted text: Mary and Gary are both doing research on the effects of sleep deprivation on critical thinking. Mary recruited 20 students. Believing that grade point average (GPA) may be a confounding variable, she divides these students into groups according to GPAS, high, medium, and low. Each member of the high GPA group was randomly assigned to one of two treatment groups, as was each member of the other GPA groups. Treatment Group 1 was administered a critical thinking exam after being deprived of sleep for 24 hours. Treatment Group 2 was administered the same critical thinking exam after receiving at least 8 hours of sleep. The exam performance of each group was compared. Gary recruited only 10 students to take part in his sleep deprivation study. In one phase of the study, all 10 students were deprived of sleep for 24 hours, after which they were administered the critical thinking exam. In the other phase of the study, the same 10 students were given a similar critical thinking exam after receiving at least 8 hours of sleep. (a) What study design did Mary use? O repeated measures design O randomized block design, blocked by GPA O independent groups design What study design did Gary use? O repeated measures design O randomized block design, blocked by GPA O independent groups design (b) Which of the following statements is an advantage of Mary's study when compared to an independent groups design? O The study design reduces the potential confounding of GPA with critical thinking ability. O The variability in the student's GPA within each block is less than the variability in the student's GPA between the blocks. O The study design produces a better estimate of the effect of sleep deprivation on critical thinking ability. O All of the above. O None of the above. (c) Which of the following statements is a disadvantage of Mary's study? O The study design requires that each treatment group use a different, but similar, version of the critical thinking exam. O The two treatment groups are independent with regards to GPA. O The study design controls for, but does not eliminate, differences in GPAS within each group. O The study design controls for, but does not eliminate, differences in GPAS between the two treatment groups. (d) Which of the following is a disadvantage of Gary's study? O The two groups are independent with regard to GPA. O The study design requires that each group use a different, but similar, version of the critical thinking exam. O The study design controls for, but does not eliminate, differences in GPAS between the two groups. O The study design controls for, but does not eliminate, differences in GPAS within each group.