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Uday
Level I

How to perform MANOVA with continuous variables which are not normally distributed (non-parametric)

I am performing an analysis of hemoglobin values at 3 different time points between cases and controls. The data is not normally distributed. How should I go about with MANOVA in such a setting? Also is there an alternative test that I can apply in JMP to see the differences in the cases & controls at these 3-time points.

4 REPLIES 4

Re: How to perform MANOVA with continuous variables which are not normally distributed (non-parametric)

How are you assessing normality? Are you assessing the response itself? The predictors?

Uday
Level I

Re: How to perform MANOVA with continuous variables which are not normally distributed (non-parametric)

Currently I had analyzed normalcy using the goodness of fit by Shapiro-Wilk test for Y variable at each time point. In my case, the distribution is not normal (p is significant in the Shapiro-Wilk test). In a situation where even at a one-time point (among the 3-time points) the distribution is abnormal, I am presuming to apply a nonparametric test.

Not sure if this is the right way of looking at the normalcy or evaluating the differences in cases and controls over the 3-time points. Please suggest.

Re: How to perform MANOVA with continuous variables which are not normally distributed (non-parametric)

I suggest that you proceed with your analysis and check the residuals for anomalies before choosing another method of analysis.

statman
Super User

Re: How to perform MANOVA with continuous variables which are not normally distributed (non-parametric)

ANOVA is fairly robust to the underlying distribution of the individual values.  As Mark suggests, go ahead with your analysis and then check residuals for assumptions NID(0, variance).

"All models are wrong, some are useful" G.E.P. Box