Refer to the data of Exercise 24 on the percentage of unionization in the fifty states.

(a) Based on the data grouping used in constructing your histogram: (i) Estimate the mean of these unionization rates. (ii) Estimate the population standard deviation for these rates. (iii) Estimate the median unionization percentage.. (iv) Estimate the interquartile range of these percentages.

(b) Now calculate the mean and standard deviation directly from the fifty observations and compare them with your answers in (a).