U Chart Diagnostic
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Stat > Control Charts > Attributes Charts > U Chart Diagnostic

Use this test to determine whether a traditional U chart or a Laney U' chart is more appropriate to chart the number of defects per unit in your sample. If the test determines that your data exhibit overdispersion or underdispersion a Laney U' chart may more accurately distinguish between common cause variation and special cause variation.

Dialog box items

Variables: Enter the columns that contain the number of defects for each subgroup.

Subgroup sizes: Enter a number or a column that contains the subgroup sizes.