Testing for overdispersion and Laney P' chart
We will use a Laney P' chart to correct the overdispersion in our data. The P chart in the previous example calculates the control limits on the binomial distribution. If the process being studied has a natural variation in the proportion that has a variation larger than the binomial distribution, then a P chart can show many more out of control points than it should. The P chart uses the variation between groups to estimate the position of the control limits.
Minitab has a P chart diagnostic tool to look for overdispersion or underdispersion in the data.
Initially, we will run the P chart diagnostic to check our data and then run the P' chart.
How to do it...
The following steps will check for overdispersion ...
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