T2 Chart
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Stat > Control Charts > Multivariate Charts > Tsquared

The T2 control chart is the multivariate version of the X chart (or the Individuals chart for individual observations). Its purpose is to assess whether several variables are simultaneously in control. For example, to monitor the quality of automobile tire casings, you can simultaneously measure three variables: weight, temperature, and percentage of polyester.

Before using a multivariate control chart, you need to make sure that a dependence exists between the variables. If you assume the variables are independent, then you do not need a multivariate control chart.

For more information, see Control Charts Overview and Multivariate Control Charts Overview.

Dialog box items

Variables: Enter at least two columns of data.

Subgroup sizes: Enter a number or a column of subscripts.  If the subgroups are not equal, each control limit is not a single straight line but varies with the subgroup size. If the subgroup sizes do not vary much, you may want to force the control limits to be constant by specifying a fixed subgroup size using Tsquared Options > Estimate.

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