Example of an Analysis of Means for Variances Chart
This example uses the Spring Data.jmp sample data table. Four different brands of springs were tested to see what weight is required to extend a spring 0.10 inches. Six springs of each brand were tested. The data was checked for normality, since the ANOMV test is not robust to non-normality. Examine the brands to determine whether the variability is significantly different between brands.
1. Select Help > Sample Data Library and open Spring Data.jmp.
2. Select Analyze > Fit Y by X.
3. Select Weight and click Y, Response.
4. Select Brand and click X, Factor.
5. Click OK.
6. Click the red triangle next to Oneway Analysis of Weight By Brand and select Analysis of Means Methods > ANOM for Variances.
7. Click the red triangle next to Analysis of Means for Variances and select Show Summary Report.
Figure 6.14 Example of Analysis of Means for Variances ChartÂ
Note that the standard deviation for Brand 2 exceeds the lower decision limit. Therefore, Brand 2 has significantly lower variance than the other brands.