The boxplot (also called the box-and-whisker plot) represents the distribution of data as a box and whiskers. It is useful for comparing the distribution of various groups of data.
1. Choose ProcessMA > Graphs > Boxplot.
2. In Data in, choose how your data is stored.
a. If your data in stored in a single column:
- In Variable, select the column containing the response
- In Category, select the column containing subgroup codes
b. If your data in stored in different columns:
- In Variables, select the columns containing the separate responses.
3. Click OK.
Optional
4. Check Show outliers, if you want to plot the outliers, which are represented as asterisks (*).
5. Check Show mean, if you want to display the subgroup means.
6. Check Connect means/medians, if you want to connect the subgroup means and medians.
Note To select a column of data into a textbox, double-click on any of the column names shown in the list on the left of the dialog box while in the textbox.
Variable: Numeric.
Category: Text or Numeric; Must have the same number of data points as the variable; Must contain at least 2 distinct categories.
Variables: Numeric.
A company makes steel bolts using four different machines. You want to assess if the dimensions of the steel bolts made by different machines are the same. You want to use Boxplot to compare the distributions.
1. Open worksheet ProcessMA > Tools > Data Files > Stat.xls.
2. Choose ProcessMA > Graphs > Boxplot.
3. In Data in, select a single column.
4. In Variable, select N – Dimension.
5. In Category, select O – Machine.
6. Check Show outliers.
7. Check Show mean.
8. Check Connect means/medians.
9. Click OK.
