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Publication date: 04/21/2023

Example of the Robust Fit Option

Use the Oneway platform with a robust fit in this example where one of three groups contains outliers. The data contain the toxicity levels for three different formulations of a drug.

1. Select Help > Sample Data Folder and open Drug Toxicity.jmp.

2. Select Analyze > Fit Y by X.

3. Select Toxicity and click Y, Response.

4. Select Formulation and click X, Factor.

5. Click OK.

6. Click the Oneway Analysis red triangle menu and select Means/Anova.

7. Click the Oneway Analysis red triangle menu and select Robust > Robust Fit.

Figure 6.28 Example of Robust FitĀ 

Example of Robust Fit

If you look at the standard Analysis of Variance report, you might conclude that there is a difference between the three formulations, since the p-value is 0.0319. However, when you look at the Robust Fit report, you would not conclude that the three formulations are significantly different, because the p-value there is 0.2175. It appears that the toxicity for a few of the observations is unusually high, creating the undue influence on the data.

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