Example of a boxplot with multiple y's
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Your company makes plastic pipes, and you are concerned about the consistency of their diameters. You measure ten pipes a week for three weeks. Create a boxplot to examine the distributions.

1    Open the worksheet PIPE.MTW.

2    Choose Graph > Boxplot.

3    Under Multiple Y's, choose Simple. Click OK.

4    In Graph Variables, enter 'Week 1'  'Week 2'  'Week 3'. Click OK.

Graph window output

Interpreting the results

Tip

To see precise information for Q1, median, Q3, interquartile range, whiskers, and N, hover your cursor over any part of the boxplot.

 The boxplot shows:

·     Week 1 median is 4.985, and the interquartile range is 4.4525 to 5.5575.

·     Week 2 median is 5.275, and the interquartile range is 5.08 to 5.6775. An outlier appears at 7.0.

·     Week 3 median is 5.43, and the interquartile range is 4.99 to 6.975. The data are positively skewed.

The medians for the three weeks are similar. However, during Week 2, an abnormally wide pipe was created, and during Week 3, several abnormally wide pipes were created.