ANOVA

Analysis of Variance

ANOVA is used to determine if the average of a group of data is different than the average of other (multiple) groups of data. This tool is used in the ANALYZE phase of a DMAIC Six Sigma project.

The Y-data is variable type of data (such as time).

The X-data is attribute data (such as appraiser name). We also were interested if there was a significant difference in two or more appraisers. The results of a mock study where four appraiser were timed to make an inspection decision on a widget.

Using a One-Way ANOVA with alpha at 0.05, we concluded there was not a statistical difference between any of the appraisers.

The P-value well above 0.05, f-statistic, and heavily overlapping confidence intervals are all evidence that there is no difference among any pairs or combinations of them.

If the P was <0.05, then at least one group of data is different than at least one other group.

The low F-value of 0.27 says the variation within the appraisers is greater than the variation between them and not within the rejection region, the F-critical value is 2.81.