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Knowledge Base » SigmaXL Toolbox

Comparing ANOVA and Boxplot Results

on January 01, 2012

How can I compare ANOVA and Boxplot results?

Comparing ANOVA and Boxplot Results

The following graph of Overall Satisfaction by Customer Type is created using One-Way ANOVA.

(Recreate this example using Customer Data.xls, included with SigmaXL as Sample Data):

Now create a Boxplot using the same data:

It may be confusing to see that the "vertical line" for each location in the ANOVA chart does not seem to represent the total spread of the data versus the Boxplot, which shows the minimum and maximum.

The graph in ANOVA shows the mean and 95% confidence intervals (with a pooled estimate of StDev), hence the vertical lines will be different from the Boxplot.

If you use the Multi-Vari chart in Graphical Tools, (SigmaXL > Graphical Tools > Multi-Vari) the vertical lines will be the same as those in the Boxplot, except when there is an outlier.

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