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Suppose that I have two IVs (AnxietyLevel & experimental conditions (dummy coded as 0 and 1), and two control variables (Age & Gender) and one DV (mean score on a questionnaire). And I am trying to find out both main and interaction effects via hierarchical regression analysis.
My models for the above in R would be:
H1 <- lm(mean_score ~ age + gender, data = df)
where gender shows a significant p-value.
However, the effect of gender becomes insignificant with the model below:
H2 <- lm(mean_score ~ age + gender + anxiety * expconditions, data = df)
So now nothing, even the interaction effect, is significant. What does this mean in plain English (if possible)?
I still cannot seem to wrap my head around it, so any help will be appreciated!!