Statistics Dictionary

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Back-to-Back Stemplots

Boys

Girls
7
1
1 4 6
4 5 8
1 2 2 2 8 9
3 4 7 9
2 5 8
1 3
0
1
2
3
4
5
6
7

1
2 6 8
3 4 4 6 6 8 9
4 3 6
4

Back-to-back stemplots are a graphic option for comparing data from two populations. The center of a back-to-back stemplot consists of a column of stems, with a vertical line on each side. Leaves representing one data set extend from the right, and leaves representing the other data set extend from the left.

The back-to-back stemplot on the right shows the amount of cash (in dollars) carried by a random sample of teenage boys and girls. The boys carried more cash than the girls - a median of \$42 for the boys versus \$36 for the girls. Both distributions were roughly bell-shaped, although there was more variation among the boys. And finally, there were neither gaps nor outliers in either group.

 See also: AP Statistics Tutorial: Comparing Distributions | AP Statistics Tutorial: Stemplots