Moderation at some levels of moderator but not in overall model

New Member
Hello

I have three continuous variables one of which I have hypothesised to be a moderator. In the overall regression model there is no significant result for the product of the IV and predicted moderator, R2 change = .00, F change (1, 118) = 0.46, p >.05. That is, there is no overall moderating effect. However, when I use the PROCESS plug in to test for possible combined effects at different levels of the hypothesized moderator, using both the pick a point and Johnson Neyman technique a moderator effect can be seen at certain levels of the moderator.

My question:
1) Is it justifiable to proceed to test for combined effects at different levels of the moderator once you have shown there is no overall moderator effect?
2) Are there published papers which explain this approach?

I have searched the forum and noted a few other people have posted similar questions but to date there have not been any suggestions as to the best way to proceed.

ondansetron

TS Contributor
Hello

I have three continuous variables one of which I have hypothesised to be a moderator. In the overall regression model there is no significant result for the product of the IV and predicted moderator, R2 change = .00, F change (1, 118) = 0.46, p >.05. That is, there is no overall moderating effect. However, when I use the PROCESS plug in to test for possible combined effects at different levels of the hypothesized moderator, using both the pick a point and Johnson Neyman technique a moderator effect can be seen at certain levels of the moderator.

My question:
1) Is it justifiable to proceed to test for combined effects at different levels of the moderator once you have shown there is no overall moderator effect?
2) Are there published papers which explain this approach?

I have searched the forum and noted a few other people have posted similar questions but to date there have not been any suggestions as to the best way to proceed.

If a joint significance test (I'm assuming what you mean by "overall significance") of the terms relating to a particular moderator is not significant, it doesn't make much sense to test any of the terms individually. The joint test answers the question "Is at least one of these terms useful for predicting the DV, all else constant?" If it's nonsignificant, you can see that the answer is no and you should only followup on a significant test.

I hope I've understood your question.