How do I interpret stem plots that are truncated or rounded like this one?

Question

Shopping spree The stemplot displays data on the amount spent by 50 shoppers at a grocery store. Note that the values have been rounded to the nearest dollar.

 

0 | 3 9 9

1 | 1 3 4 5 6 7 7 8 8 9

2 | 0 0 0 1 2 3 4 5 6 6 8 8 8 8

3 | 2 5 6 9 9

4 | 1 3 4 5 5 7 9

5 | 0 3 5 9

6 | 1

7 | 0

8 | 3 6 6

9 | 3

 

Key 9|3 = 92.50 to 93.49 spent

 

a. What was the smallest amount spent by any of the shoppers?

b. Describe the distribution of amount spent by these 50 shoppers.

Answer 1

(a) The stem is the tens unit for the plot, so 03 or $3 is the lowest amount. Because of rounding, this could be $2.50.

(b) The right tail is longer than the left tail of the plot so it’s a distribution with positive skew. The mean is greater than the median. That is, many more shoppers spend comparatively less than those that spend a lot.