Figure 4. Stem and leaf display with negative numbers and rounding.
Observe that the figure contains a row headed by “0” and another headed by “-0.” The stem of 0 is for numbers between 0 and 9, whereas the stem of -0 is for numbers between 0 and -9. For example, the fifth row of the table holds the numbers 1, 2, 4, 5, 5, 8, 9 and the sixth row holds 0, -6, -7, and -9. Values that are exactly 0 before rounding should be split as evenly as possible between the “0” and “-0” rows. In Table 2, none of the values are 0 before rounding. The “0” that appears in the “-0” row comes from the original value of -0.2 in the table.
Although stem and leaf displays are unwieldy for large data sets, they are often useful for data sets with up to 200 observations. Figure 5 portrays the distribution of populations of 185 US cities in 1998. To be included, a city had to have between 100,000 and 500,000 residents.
4|899
4|6
4|4455
4|333
4|01
3|99
3|677777
3|55
3|223
3|111
2|8899
2|666667
2|444455
2|22333
2|000000
1|88888888888899999999999
1|666666777777
1|444444444444555555555555
1|2222222222222222222333333333
1|000000000000000111111111111111111111111111
Figure 5. Stem and leaf display of populations of 185 US cities with populations between 100,000 and 500,000 in 1988.
Since a stem and leaf plot shows only two-place accuracy, we had to round the numbers to the nearest 10,000. For example the largest number (493,559) was
80
