XBar and S Charts with Varying Subgroup Sizes Example

This example uses the Coating.jmp data table. This quality characteristic of interest is the Weight 2 column.

1. Select Help > Sample Data Library and open Quality Control/Coating.jmp.

2. Select Analyze > Quality and Process > Control Chart Builder.

3. Drag Weight 2 to the Y role.

4. Drag Sample to the Subgroup role (at bottom).

Figure 3.20 XBar and S Charts for Varying Subgroup Sizes 

Weight 2 has several missing values in the data, so the chart has uneven limits. Although each sample has the same number of observations, samples 1, 3, 5, and 7 each have a missing value.

Instead of viewing a line connecting the averages of each sample, you can switch to viewing box plots at each sample.

5. In the Points[1] outline, deselect the Show Connected Line option.

6. In the Points[1] outline, select the Box Plots option.

Figure 3.21 XBar and S Chart with Box Plots