Probability Plot

Overview | How to | Example

Overview

This can be used to display a probability plot for variables.

How to

At the Excel Menu (For Excel 2007, go to Add-ins first)

1. Choose ProcessMA > Graphs > Probability Plot

2. In Variable, select the column containing the data (Numeric)

3. In Distribution, choose the distribution to fit

4. In Confidence Level, enter the desired confidence level (Numeric, >0 & <1)

5. Check Show Confidence Interval, if you want to display confidence interval in the probability plot

6. Enter the know historical parameters for the respective distribution is required (Optional, Numeric)

7. Click OK

Example

You work in a manufacturing plant making widgets and you collected failure times for 50 widgets. You want to determine if a Normal distribution fits your data.

1. Open data worksheet by choosing ProcessMA > Tools > Data

2. In Variable, select CD - Failure Times

3. In Distribution, choose Normal

4. Check Show Confidence Interval

5. Click OK

Results & Interpretation

The data fits a normal distribution with mean of 161.6 and standard deviation of 21.527 fairly well.

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