During the Spring 2009 semester, 200 students took a statistics test from a particular instructor. The resulting grades are given in the following table.
Test grades Number
50–60........ 13
60–70........ 44
70–80........ 74
80–90........ 59
90–100........ 9
100–110........ 1
Total ........ 200
a. What is the class width?
b. Draw and completely label a frequency histogram of the statistics test grades.
c. Draw and completely label a relative frequency histogram of the statistics test grades.
d. Carefully examine the two histograms in parts b and c and explain why one of them might be more useful to a student and to the instructor.