I am currently doing research with an independent variable (four treatment groups), a continuous dependent variables, 5 control variables, and 2 continuous moderators. I figured out that I needed to do an ANCOVA analysis with the 5 control variables as covariates and the treatment groups as factor. I just cannot figure out how I can include the moderating variables into the analysis. Do I put them into the analysis as covariates (moderator1 & moderator1*treatment & moderator2 & moderator2*treatment) or should I do this differently, for instance not including the interaction variables?
ANCOVA with moderators
- Thread starter sverm
- Start date
- Tags ancova moderators
If you don't include the interaction variables you won't be able to test for moderation. So, if you don't want to use moderating varaibles as covariates (which to be honest, I am not sure if you should do or not), I can think of 2 options.:
1. Use a regression analysis. Problem is, you will have to turn your IV into dummy variables and use 15 different interaction variables.
2. Transform each continuous variable into an ordinal variable, with only a few possible values. Problem is, you will lose resolution. Plus, you need a big sample. However, this comes with a benefit - you will be able to detect non-linear patterns, if they exist.
1. Use a regression analysis. Problem is, you will have to turn your IV into dummy variables and use 15 different interaction variables.
2. Transform each continuous variable into an ordinal variable, with only a few possible values. Problem is, you will lose resolution. Plus, you need a big sample. However, this comes with a benefit - you will be able to detect non-linear patterns, if they exist.
Thank you for your response. I will probably do a regression analysis with dummy variables then. I already did turn my IV into dummy variables. I don't fully understand how you came up with 15 different interaction variables. I should multiply my moderator with each dummy variable, right? So then I'll have 2(moderators)*4(treatment groups) = 8 interaction variables, or did I understand it wrong? Thanks in advance!!
You will have 3 dummy variables and 2 moderators. That is 6 2-way interactions. However, to truly understand the relationship between the variables you will have to also calculate another 3 3-way interactions. 9 in total (not 15, which for some reason seemed logical to me as I wrote my previous message)