I am doing a project, where I have conducted a randomised controlled trial. I test if I can get the same results of an already published paper, but in another setting. In my created setting, I have one control group, and 5 treatment groups. The published paper got significant differences between all treatment groups and the control group separately. There is no explanation of the statistical method used in the paper.
Which statistical method is best for testing the difference between all of my treatment groups and the control group, separately? Meaning: Treatment 1 versus control, Treatment 2 versus control, etc.
Right now, I am using linear contrasts in an ANOVA framework, which only provides significant differences between one of the treatment groups and the control group (which is okay and somewhat expected).
However, I want to make sure that I can control for the effect of age, gender, and occupation. Do I use a multiple regression to do that? Does it make sense to make ANOVA’s linear contrasts to test mean differences, and then follow it up with a multiple regression?
PS: When I make the multiple regression now, I get different significance results compared to the linear contrasts in ANOVA. Does this mean anything?