Overview for Xbar Chart

Use Xbar Chart to monitor the mean of your process when you have continuous data in subgroups. Use this control chart to monitor process stability over time so that you can identify and correct instabilities in a process.

For example, a plastics manufacturer wants to determine whether the production process for a new product is in control. The manufacturer collects subgroups of 5 units every hour for 20 hours and assess the strength of the plastic. The points vary randomly around the center line and are within the control limits. No trends or patterns are present. The strength of the plastic product is stable across the 20 subgroups.

Where to find this control chart

  • PC: STATISTICS > Control Charts > Continuous > Xbar
  • Mac: Statistics > Continuous > Xbar

When to use an alternate control chart

  • If you do not have subgroups, use Individuals Chart.
  • If your data are counts of defectives or defects, use an attribute control chart, such as P Chart or U Chart.
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