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tips:multiple_factors_interactions

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tips:multiple_factors_interactions [2021/10/22 14:44]
Wolfgang Viechtbauer
tips:multiple_factors_interactions [2021/11/10 20:20] (current)
Wolfgang Viechtbauer
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 We have also not yet tested whether there is a difference between levels ''some'' and ''high'' of this factor. One could change the reference level of the ''weeks'' factor and refit the model to obtain this test. Alternatively, and more elegantly, we can just test the difference between these two coefficients directly. We can do this with: We have also not yet tested whether there is a difference between levels ''some'' and ''high'' of this factor. One could change the reference level of the ''weeks'' factor and refit the model to obtain this test. Alternatively, and more elegantly, we can just test the difference between these two coefficients directly. We can do this with:
 <code rsplus> <code rsplus>
-anova(res.a1, L=c(0,1,-1,0))+anova(res.a1, X=c(0,1,-1,0))
 </code> </code>
 <code output> <code output>
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 Now, the table with the model results directly provides the estimated average effect for each factor level combination. It is now also quite easy to test particular factor level combinations against each other. For example, to test the difference between levels ''some'' and ''high'' of the ''weeks'' factor within the ''blind'' level of the ''tester'' factor, we could use: Now, the table with the model results directly provides the estimated average effect for each factor level combination. It is now also quite easy to test particular factor level combinations against each other. For example, to test the difference between levels ''some'' and ''high'' of the ''weeks'' factor within the ''blind'' level of the ''tester'' factor, we could use:
 <code rsplus> <code rsplus>
-anova(res.i2, L=c(0,1,-1,0,0,0))+anova(res.i2, X=c(0,1,-1,0,0,0))
 </code> </code>
 <code output> <code output>
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 To test the same contrast within the ''aware'' level of the ''tester'' factor, we would use: To test the same contrast within the ''aware'' level of the ''tester'' factor, we would use:
 <code rsplus> <code rsplus>
-anova(res.i2, L=c(0,0,0,0,1,-1))+anova(res.i2, X=c(0,0,0,0,1,-1))
 </code> </code>
 <code output> <code output>
tips/multiple_factors_interactions.txt ยท Last modified: 2021/11/10 20:20 by Wolfgang Viechtbauer