How do I perform multiple comparison tests (on the means) when you have unequal variancesLet's say you are running a One-way ANOVA with 5 groups. You test for equal variance and conclude that the assumption of equal variance does not hold. You then evaluate Welch's test. The p-value from Welch's test indicates that the 5 group means are not equal. Is there a simple way to run a multiple comparison test (to compare the 5 means or a Dunnett's like test to compare 4 of the means to a control group) when you have unequal variance?
Ideally, this would be an option found in the "red triangle" when using Fit Y by X (for the One-way ANOVA case). Perhaps found in the Compare Means choices (see attached for a possible example).
Thanks
Basic Data Analysis and ModelingRe: How do I perform multiple comparison tests (on the means) when you have unequal variancesA modified suggestion is, once the variances are found not to be equal, to allow modeling of the variance as function of the mean, then re-test homogeneity of the model-estimated variances. Then the means comparison is done as before but using the modeled variances.
Re: How do I perform multiple comparison tests (on the means) when you have unequal variancesPerfect! Thank you for your help.
Re: How do I perform multiple comparison tests (on the means) when you have unequal variancesHi Rich,
Give this a try. It at least covers the Turkey HSD situation. I just updated the add-in a couple days ago.
https://community.jmp.com/t5/JMP-Add-Ins/Games-Howell-Test-Tukey-HSD-with-Welch-s-correction-for-Unequal/ta-p/213771
