Students want to determine if there is a significant correlation between the amount of free time spent using their cell phones and their GPA. Determine the type of study used in each examples (a-c) below.
a)
Part A
(a.) 50 students were selected randomly and asked about the number of hours they spent in a week using their phones and their current GPA.
Part B
(b.) The GPA's of 50 randomly selected students that do not own cell phones were recorded and compared to 50 randomly selected students with cell phones and their
GPA's.
Part C
(c.) Ten students with poor GPA's had their cell phones restricted for a year. After the year their current GPA was compared with their GPA from the previous year.
Part D
Which of the above examples (a-c) would you suggest be used for the study? Explain your reasoning.