Book Image

Minitab Cookbook

By : Isaac A Newton
Book Image

Minitab Cookbook

By: Isaac A Newton

Overview of this book

Table of Contents (19 chapters)
Minitab Cookbook
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

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 in the data and then generate a P' chart:

  1. Use Open Worksheet… from the File menu to open the Calls Lost.mtw worksheet.

  2. Navigate to Stat | Control Charts | Attributes Charts and select P Chart Diagnostic.

  3. Enter Hung up in the Variables: field.

  4. In...