X Chart
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Stat > Control Charts > Variables Charts for Subgroups > Xbar

A control chart of subgroup means. You can use X charts to track the process level and detect the presence of special causes.

By default, Minitab's X chart estimates the process variation, s, using a pooled standard deviation. You can also base the estimate on the average of the subgroup ranges or standard deviations, or enter a historical value for s.

You can set options for control charts in all Minitab sessions using Tools > Options > Control Charts and Quality Tools. Available options include how to estimate s, test definitions, and what tests to perform. When you set options, all affected dialog box settings automatically reflect your preferences.

For more information, see Control Charts Overview and Variables Control Charts for Subgroups Overview.

Dialog box items

All observations for a chart are in one column: Choose if data are in one or more columns, then enter the columns.  

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 Xbar Options > Limits.

Observations for a subgroup are in one row of columns: Choose if subgroups are arranged in rows across several columns, then enter the columns.

<Scale>

<Labels>

<Multiple Graphs>

<Data Options>

<Xbar Options>