Why should you keep the space? Suppose that you had a data set for girls similar to the one given in Example 3.10, but that the observations of 33 ng/ml and 34 ng/ml were both changed to 35 ng/ml.

(a) Make a stemplot of these data for girls only using split stems.

(b) Should you use one stem or two stems for the 30s? Give a reason for your answer.

EXAMPLE 3.10

Vitamin D. Your body needs vitamin D to use calcium when building bones. It is particularly important that young adolescents have adequate supplies of this vitamin because their bodies are growing rapidly. Vitamin D in the form 25-hydroxy vitamin D is measured in the blood and represents the stores available for the body to use. The units are nanograms per milliliter (ng/ml) of blood. Here are some values measured on a sample of 20 adolescent girls aged 11 to 14 years:

To make a stemplot of these data, use the first digits as stems and the second digits as leaves. Figure 3.6 shows the steps in making the plot. The girl with a measured value of 16 ng/ml for vitamin D appears on the stem labeled 1 with a leaf of 6, while the girl with a measured value of 43 ng/ml appears on the stem labeled 4 with a leaf of 3.

The overall pattern of the data is fairly regular. The lowest value, 16 ng/ml, is somewhat lower than the next highest value, 23, but it is not particularly extreme.