X bar S Chart Excel

Use an X bar S Chart (Average and Stdev Chart) to Evaluate Stability of Processes Using Variable Data

Here is an example of an X and Standard Deviation chart created using QI Macros for Excel.

x and s or x and standard deviation chart example using QI Macros

The X bar S chart can help you evaluate the cycle time for almost any process: making a widget, answering a customer call, seating a customer, delivering a pizza, or servicing an appliance. This chart is especially useful when you do this many times a day. Collecting the data could be expensive if you measured every time you did it. Using a small sample (typically 6 or more), however, you can effectively measure and evaluate the process.

Calculate, plot, and evaluate the standard deviation (S) chart first. If it is "out of control," so is the process. If the S chart looks okay, then calculate, plot, and evaluate the X chart.


Tip: QI Macros will prompt you for your subgroup size. A subgroup is a group of measurements produced under the same set of conditions. In the example above the subgroup size is five.

Note: The XbarS Chart in QI Macros was developed to support a maximum of 800 columns of data.

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