Example of a boxplot with groups
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You want to assess the durability of four experimental carpet products. Samples of the carpet products are placed in four homes and you measure durability after 60 days. Create a boxplot with median labels and color-coded boxes to examine the distribution of durability for each carpet product.

1    Open the worksheet CARPET.MTW.

2    Choose Graph > Boxplot.

3    Under One Y, choose With Groups. Click OK.

4    In Graph variables, enter Durability.

5    In Categorical variables for grouping (1-4, outermost first), enter Carpet.

6    Click Labels, then click the Data Labels tab.

7    From Label, choose Medians. Choose Use y-value labels. Click OK.

8    Click Data View.

9    In Categorical variables for attribute assignment, enter Carpet. Click OK in each dialog box.

Graph window output

Interpreting the results

Median durability is highest for Carpet 4 (19.75). However, this product also demonstrates the greatest variability, with an interquartile range of 9.855. In addition, the distribution is negatively skewed, with at least one durability measurement of about 10.

Carpets 1 and 3 have similar median durabilities (13.52 and 12.895, respectively). Carpet 3 also exhibits the least variability, with an interquartile range of only 2.8925.

Median durability for Carpet 2 is only 8.625. This distribution and that of Carpet 1 are positively skewed, with interquartile ranges of about 5-6.