Six Sigma SPC - Statistical Process Control

Six Sigma SPC's Quality Control Dictionary and Glossary
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X Bar - Mean - Average

X Bar is an average of a sample. It is the arithmetic mean. It is calculated by adding the observation, (subgroup using stratified sampling), values and dividing by the total number of samples. This data is typically charted on a line control chart with the center line being X Double Bar, (an average of the averages), and upper control limits and lower control limits. You can also use Pre-Control to establish control limits.

We use averages because they are more susceptible to change than single values. To see how to use this chart, see statistical process control overview and the X-Bar and R-Bar explanation pages.

x is an individual observation
is the total number of samples

X Bar  = x1 + x2 + x3 + x4 .... xn



X Bar = (.05 + .05 + .051 + .049 + .05) / 5
X Bar = .05

For an example of a X Bar charts see our ZeroRejects features page. It makes doing statistical process control and six sigma charts easy. And at only $150.00, (USD), our software can get you going quickly.

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Last Updated: Wednesday, 17-May-06 10:21:09 PDT