Question

Which intervals are most appropriate for constructing a frequency table for the data set? 
45   53   60   36   22   27   47   68   33   51   55   29   28   45   43

A.) 20–39, 40–49, 50–59, 60–69


B.) 20–35, 35–50, 50–65, 65–80


C.) 20–34, 35–49, 50–64, 65–79


D.) 20–39, 40–54, 55–65, 66–75

Answer 1

There are a few criteria one can use for choosing intervals.

1. make the intervals as uniform as possible
2. cover the range in a "reasonable" number of intervals
3. appropriately reflect the data distribution
4. make the boundaries unambiguous

Selection B has boundaries that overlap, so can be ruled out immediately. Selection D has ranges that go from 19 to 9, so does not have very uniform intervals. Likewise, selection A defines the first interval to be twice the width of the others, so it isn't a good choice, either.

IMO, the best of the offered choices is ...

... C.) 20–34, 35–49, 50–64, 65–79