Interactions in OLS regression and simple slopes.

[#1]

Hey everyone,

I am currently trying to perform an OLS (linear) regression model with an interaction effect (to test for moderation). For example, let's say I wish to predict a continuous variable Y using two continuous variables X and M and their interaction X*M.

The result of the effect of the interaction term is significant. However, I do not know how to ask JMP to give the data for the simple slopes. 

Specifically, how do I get the betas and their significance for the effect of X an Y at the different levels of M? (usually -1sd, mean, 1sd for continuous variable or if the moderator is binary than at both levels of the moderator).

I know how to get the plots (Fit model ... Full factorial etc.), but it's not enough, I need the actual simple effects for the slopes, SE and significance. 

Will appreciate any help on the matter. 

[#2]

Thanks @Dan_Obermiller 

Just 1 more question. If I understand correctly, the red horizontal line is the predicted value of the DV, while the Shaded part is the CI for the predicted VL. If so, can you help me to understand why when the horizontal line stays inside the Shaded CI, the results is NOT significant?

[#3]

When the horizontal line is all within the confidence interval, the factor is not significant as the effect of that factor could easily be zero (no slope). Therefore, not significant.

[#4]

@YaM @nguyentandat234I'm happy to share that one of our summer interns, @haley.yaremych who is also a PhD student at Vanderbilt, wrote an add-in for moderation and moderated mediation and is now available in the JMP community. She’s also written an excellent blog post with examples to illustrate how to use it:

Who, what, why, and how? Tools for modeling and visualizing moderation and moderated mediation in JM...

The add-in requires JMP Pro 16.0 or higher. Here's a preview of her Johnson-Neyman plot, which has interactivity to show the simple slope and its statistical significance at each value of the moderator:

I hope this will be useful for your work!

~Laura