Most of the problems in this and other chapters deal with "real" data for which computations are most efficiently performed with computers. Since a little experience in manual computing is healthy, here are 15 observations of a variable having no particular meaning:

12   18   22   17   20   15   19   15   19   13   23   8   14   14   19  11  30

(a) Compute the mean, median, variance, range, and interquartile range for these observations.

(b) Produce a stem and leaf plot.

(c) Write a brief description of this data set