Hello, I have a question about ANCOVA. I have two factors: gender and group (intervention and control), one covariate. It is suggested that I should use three-way ANOVA to analyze the difference between groups after controlling the age and gender. But the assumption is very complex. Can I use the ANCOVA with two factors to conduct the analysis?
The problem has been solved. Thank you very much!
See the Montgomery's Design and Analysis of Experiments the ANCOVA Section for details which is available in the z-library. Google it. Best wishes, David Booth
Since age is not categorical (discrete), you are not allowed to conduct three-way ANOVA in this case.
Hello Chao,
Is age the covariate? It's not clear from your query where/what age represents.
Does your research question specifically address age as a possible influence? If not, I'm not sure why you'd want to add it to your set of independent variables (regardless of whether you treated it as a continuous variable, like a covariate, or as a block variable). Either way, you may include it; that isn't the same as saying you ought to include it.
If age is the covariate, you're likely better treating it as a continuous variable than by treating it as a block variable (with each level representing some interval of ages: e.g., 21-25).
I would suggest that consulting a good design text, as suggested by Professor Booth, might be a good idea.
Good luck with your work.
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