Hiiiii everyone!
I have an enquiry on statistical analysis. I was looking for many forum and it's still cannot solve my problem.
I want to compare means of two groups of data but only with two measurements. For example:
Treatment A:
Before treatment
After treatment
Treatment B:
Before treatment
After treatment
For the case, I would like to compare is it have any significance between two groups. But I couldn't use One-way ANOVA since it only have two measurement.
Hope anyone can help me! Thank you vey much!!!
You can run an ANCOVA (analysis of covariance), i.e. a regression:
Post = Pre + Treatment/Group (in that order). The assumption is that there is no interaction between 'Pre*Group'. i.e. the heterogeneity of slopes.
If this assumption is not met, you can use the Johnson-Neyman technique to remediate.
https://kenstoyama.wordpress.com/2018/01/21/the-johnson-neyman-tecnique-and-an-r-script-to-apply-it/
Thank you for your response. I will try to have the ANCOVA test. The link is much helpful!!!
You can use simple regression and represent each treatment by a 1-0 dummy variable, which would be arithmetically equivalent to ANCOVA.
FYI, the 2-category equivalent of ANOVA is a t-test, so there is nothing wrong with running a 2-category ANOVA.
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