7 votes

Frank Harrell's interpretation of interaction in regression results

There are several examples in the help file for the contrast function in the R rms package here. An expansion of this answer is ...
Frank Harrell's user avatar
6 votes

How do I interpret low subgroup interaction and high efficacy in only one group?

Welcome to CV. There are a few errors in your analysis, or, rather, in your interpretation of your analysis. First, you tested interpretation and found it was not significant. You concluded that the &...
Peter Flom's user avatar
  • 117k
6 votes

Rstudio metafor moderator analysis: one variable is missing in Model Results + eliminating intrcpt?

This is expected behavior. The categorical moderator works in the same way as a categorical (dummy coded) predictor dies in regression, it's just that in meta-analysis the outcome is an effect, so it'...
Jeremy Miles's user avatar
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5 votes

Frank Harrell's interpretation of interaction in regression results

The quoted comment is about interpreting coefficients in a model with interaction terms. The interaction effect is one type of nonlinear effects. Common interaction terms are two-way between two ...
DrJerryTAO's user avatar
  • 1,464
5 votes

How do I interpret low subgroup interaction and high efficacy in only one group?

The Dangers of P-Value Hunts Peter already noted issues in your interpretation that I completely agree with (see my answer here, here, or here, which all show how meaningless $p$ values can become ...
Shawn Hemelstrand's user avatar
3 votes

Ordinal independent variable (IV) and continuous dependent variable (DV)

You should use the DV that you want to analyze. There is no need for the DV and IV to be on the same scales, or have the same range, or anything else like that. Questions about how to use SPSS (or any ...
Peter Flom's user avatar
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3 votes

How to interpret a nonsignificant interaction effect with significant main effects?

Your study objective is to assess effects of four drugs on a health outcome with reference to the effect of a control substance on a health outcome. It is not about influence of time on drug or drug ...
DrJerryTAO's user avatar
  • 1,464
2 votes

Three-way interaction terms

The general rule is to include all the lower level effects from an interaction. So, you include all the main effects, and all the two way interactions when you have a three way interaction. This is ...
Peter Flom's user avatar
  • 117k
2 votes
Accepted

How to calculate probability from logistic regression using interaction effect parameter?

The formula is accurate even when there are interactions. You can define a new variable as the product of two others (or more than two). Suppose you have two variables $X_1$ and $X_2$ and want to ...
Peter Flom's user avatar
  • 117k
2 votes

Multiple linear regression slopes inconsistent with graph - why?

I don't think the model is coded the way you think it is. > contr.sum(factor(0:1)) [,1] 0 1 1 -1 > contr.treatment(factor(0:1)) 1 0 0 1 1 The ...
Thomas Lumley's user avatar
1 vote

How can I test whether a moderation effect is only present due to confounding variables?

You can include them by ... well, by including them. Let's call the trait $X_1$ and the moderator $M$ and the confounders $X_2 \dots X_P$. Then: Moderated regression without confounders: $Y~X_1 + M + ...
Peter Flom's user avatar
  • 117k
1 vote
Accepted

Is It valid to use a Linear Mixed effect Model to quantify a group 'summary' value and plot it when the factors are all categorical?

You seem to have started on the right path, but there are some potential missteps to avoid. I'll assume that you have found that the assumptions underlying the model have been met adequately. With ...
EdM's user avatar
  • 90.7k

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