(KnowWare International: Denver) -- The QI Macros SPC Software for Excel announces the addition of Levene's Test of variance in normal and non-normal data. One of the keys to Six Sigma in manufacturing and service industries is the reduction of variation. To do this, employees compare two or more methods, machines or materials to find the optimum. While the standard statistical F-test can evaluate differences in variability between two samples of normal (i.e., "bell shaped") data, Levene's test can evaluate variation across two or more samples of non-normal data. What is an example of non-normal data? Skewed (i.e., leaning) data like customer wait times in a bank: most are close to a minute or less, but a few may take 25 minutes or more.

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