# Two-way MANOVA vs. two-way ANOVA on a composite variable

Is using a 2 way MANOVA to check whether height and weight differ across age groups and gender, the same as using a 2 way ANOVA to check whether BMI (wt in kg/ht in m$^2$) differ across age groups and gender?

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A side-remark. You asked 14 questions in the last several days, and several (though admittedly only few) of them seem to have received good answers. As you never "accepted" any answers on StackExchange, I guess that you might be unfamiliar with the system; so let me point out that if you received a satisfying answer you should consider "accepting" it by clicking on a green tick sign nearby. Having zero acceptance rate will likely prevent people from answering your questions. –  amoeba Jul 28 '14 at 17:05
Adding on to what @amoeba said: you should also consider upvoting answers that you like (whether or not you accept them, whether or not you asked the original question) by clicking the up arrow to the top left of the answer. –  Alexis Jul 28 '14 at 17:34

Important caveat is that statistical inferences (frequentist hypothesis testing, or confidence intervals) on transformed variables do not apply to statistical inferences on untransformed variables, because $f(\sigma^{2}_{x}) \ne \sigma^{2}_{f(x)}$. –  Alexis Jul 28 '14 at 17:32