For 15 respondents, data have been gathered on four variables (see the following table).

a. Find and report the appropriate measure of central tendency for each variable.

b. (This problem is optional.) For the variable age, construct a frequency distribution with interval size 5 and the first interval set at 15–19. Find the mean and median for the grouped variable and compare with the value for the ungrouped variable. How accurate is the estimate of the mean and median based on the grouped data?