The MANOVA method, a multivariate analysis variant, as the name says, is used when there are multiple dependent variables. The method of MANOVA in statistics is used when there are two or more two variables for calculating the mean. My approach would be to make a whole lot of simplifying assumptions, and make them on the conservative side (so your power is underestimated, rather than overestimated), and then run a simulation. MANOVA stands for multivariate analysis variance. SEMs make specifying the model and estimating the power much easier, and you can use a free package like Lavaan (which is part of R).įinally, you can run a simulation, and you can do that in any software you like. Second, you can use a structural equation modeling (SEM) approach. This could be written in any program, but I've never seen it implemented anywhere else. SPSS has a power option in manova, which is a bit weird and useless (because it's a transformation of the p-value. I know of three approaches to getting the power - first, you can use the SPSS MANOVA function (if you have SPSS). You need to consider that you will be looking at univariate tests and multivariate tests, and for the multivariate tests you need to worry about the sphericity assumption, if that will be violated, if you will use a correction, or if you will use the lower bound estimates. You also need to consider the correlations between the predictors, and you have 8 predictors (5 dummy coded, three continuous) so there are 36 correlations (or covariances, plus 8 variances) that you need to specify. power of manova is affected by the consistency of the effects across predictors and the correlations between the outcome variables - and the correlations between the outcomes isn't something that's often thought about. Calculates the sample size for the one way MANOVA test, based on the number of groups and number of dependent variables and draw a power analysis chart. Specifying a power analysis for a manova (or mancova, same thing really) is hard because there are so many things to think about, and some of these don't get reported in the output.
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