Example of the Pareto Plot Platform

This example uses the Failure.jmp sample data table, which contains failure data and a frequency column. It lists causes of failure during the fabrication of integrated circuits and the number of times each type of defect occurred. From the analysis, you can determine which factors contribute most toward process failure.

1.	Select Help > Sample Data Library and open Quality Control/Failure.jmp.

2.	Select Analyze > Quality and Process > Pareto Plot.

3.	Select failure and click Y, Cause.

This column lists the causes of failure and is the variable that you want to inspect.

4.	Select N and click Freq.

This column list the number of times each type of defect occurred.

Click OK.

Pareto Plot Report Window

The left axis represents the count of failures, and the right axis represents the percent of failures in each category. The bars are in decreasing order with the most frequently occurring failure to the left. The curve indicates the cumulative failures from left to right.

6.	Select Label Cum Percent Points from the red triangle menu next to Pareto Plot.

Note that Contamination accounts for approximately 45% of the failures. The point above the Oxide Defect bar shows that Contamination and Oxide Defect together account for approximately 71% of the failures.

7.	From the red triangle menu, deselect Label Cum Percent Points and Show Cum Percent Curve.

8.	Double-click the y-axis labeled N and rename it Count.

9.	Double-click the y-axis to display the Y Axis Specification window.

‒	In the Maximum field, type 15.

‒	In the Increment field, type 2.

‒	In the Tick Marks and Grid Lines area, select Grid Lines for the Major grid line.

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Click OK.

10.	From the red triangle menu, select Category Legend.

Pareto Plot with Display Options

Pareto Plot with Display Options shows counts now instead of percents, and has a category legend. The vertical count axis is rescaled and has grid lines at the major tick marks.

11.	To view the data as a pie chart, select Pie Chart from the red triangle menu.

Pareto Plot as a Pie Chart

Contamination and Oxide Defect clearly represent the majority of the failures.

Launch the Pareto Plot Platform

Launch the Pareto Plot platform by selecting Analyze > Quality and Process > Pareto Plot.

The Pareto Plot Launch Window

The Pareto Plot launch window contains the following options:

Y, Cause

Identifies the column whose values are the cause of a problem. It is called the process variable and is the variable that you want to inspect.

X, Grouping

Identifies the grouping factor. The grouping variable produces one Pareto plot window with side-by-side plots for each value. You can have no grouping variable, one grouping variable (see One-Way Comparative Pareto Plot Example), or two grouping variables (see Two-Way Comparative Pareto Plot Example).

Weight

Assigns a variable to give the observations different weights.

Freq

Identifies the column whose values hold the frequencies.

Identifies a variable to produce a separate analysis for each value that appears in the column.

Threshold of Combined Causes

Enables you to specify a threshold for combining causes by specifying a minimum rate or count. Select the option and then select Tail % or Count and enter the threshold value. The Tail % option combines smaller count groups against the percentage specified of the total (combined small groups count/total group count). The Count option enables you to specify a specific count threshold. For an example, see Threshold of Combined Causes Example.

Per Unit Analysis

Enables you to compare defect rates across groups. JMP calculates the defect rate as well as 95% confidence intervals of the defect rate. Select the option and then select Constant or Value in Freq Column and enter the sample size value or cause code, respectively. The Constant option enables you to specify a constant sample size on the launch window. The Value In Freq Column option enables you to specify a unique sample size for a group through a special cause code to designate the rows as cause rows.

Although causes are allowed to be combined in Pareto plots, the calculations for these analyses do not change correspondingly.

For examples, see Using a Constant Size across Groups Example and Using a Non-Constant Sample Size across Groups Example.