7. In one mathematics class, the number of students who have different GPAs are listed in the following table: GPA Number of students 0.0 3 1.0 9 2.0 15 3.0 10 4.0 13 Total a. If we regard these students as a sample, what are the mean GPA and the sample standard deviation? b. If we regard these students as a population, what are the population mean, standard deviation