45. (Class Exercise) Each student should bring ten coins to class The observation for each coin is its age. the difference between the current year and the year on the coin.

a) Using all the students' observations, the class should construct a stem and leaf plot of the ages. What is its shape?

b) Now each student should compute the mean for that student's ten coins, and the class should construct a plot of the means. What type of distribution is this, and how does it compare to the one in (a)?

c) What concepts does this exercise illustrate? (Note: For a wide variety of activities that illustrate basic concepts of statistics, see the highly innovative text by Scheaffer et al., 1996.)