# interaction effect

1. ### Two-way partially crossed design - model selection and inference

I have data from an ecological experiment featuring a partially crossed design. The experiment manipulated air temperature (3 levels: T1, T2, T3) and precipitation (2 levels: W1, W2). However, the T2-W2 treatment combination was not performed. We have a number of response variables (e.g. plant...
2. ### How is conditional main effect interpreted when there is interaction?

I have a question about multiple regression. May I kindly ask how should I interpret the conditional main effect when the interaction is 0 and the coefficients have opposite signs, more specifically if one of the interaction term contains zero such as angle or time. Please see an example...
3. ### How to interpret coefficients for multivariate regression model if main effect is either significant or not while the interaction is significant?

Dear All, I have performed multiple regression model which consists of main effects and interactions. May I kindly ask how should I interpret the equation in case the main effect is either not significant or significant while interaction is significant. Please see my end model and equations...
4. ### SPSS: Testing moderating effect in binary logistic regression

Hey, I presume the answer to my question is fairly straightforward but im really having a hard time understanding how to approach this. I am conducting a binary logistic regression with dependent variable Conversion (0 = No, 1 = Yes) and three independent variables; Group (Control vs...
5. ### How to deal with non-proportional hazard Cox models?

Dear all, I want to run a Cox model to see if there is an interaction between two treatments. However, the test to see if proportional hazard is respected suggests that it is actually not respected. So I don't know what other statistical survival analysis to do because it means I cannot rely on...
6. ### Logistic regression for factorial design: interaction and main effects of treatments

Hi, This is my first post here. I'm hoping to get some help/feedback for the following hypothetical problem: I have a factorial experimental design with 4 groups: (1) Controls, (2) Treatment A, (3) Treatment B, and (4) Both treatments A and B. A total of 100 patients were randomly allocated in...
7. ### Subgroup based on baseline of dependend variable?

Hello everybody, I am currently working on a study with heart patients. I have no data yet but am trying to write up my methodology and am currently thinking about how to do the statistics to evaluate my hypothesis. I am a bloody beginner in regards to statistic and would be thankful for any...
8. ### What statistical test do I need to use for a moderator variable?

For my study, I'm trying to test whether a variable acts as a moderator between the relationship of two other variables. I read that I should use moderational multiple regression with an interaction effect. However, I heard you can only use it if the moderator variable has 2 categories/ is...
9. ### formula for factorial ANOVA interaction effect

Good day. I have a question regarding the formula for calculating interaction effects. In Andy Field book he gives: SSa×b = SSmodel − SSa − SSb, where a and b are the different factors in our model. What happens when we have 3 or more factors? Is this then: SSa×b×c = SSmodel - SSa - SSb - SSc...
10. ### How to interpret interaction effects when main effects are also significant

Hi! I am currently writing my thesis, and stumbled upon a problem. I am testing an hypothesis in which I examine an interaction effect. Unfortunately, both the main effect and the interaction effects are significant (see image below). Right now I don't know what to report. So my questions are...
11. ### Three-way interactions with longitudinal data

Hi there, We are trying to examine whether carrying the risk gene for Alzheimer's disease (E4), moderates the effect of a continuous predictor over time (c.RNT#c.Time), on global cognition. In other words, "does carrying (or not carrying) the E4 allele moderate the effect of RNT on global...
12. ### R lme4: Plotting three-way interaction / conditional coefficient plot

Hi all, I'm trying to visualize a three-way interaction from a rather complex linear mixed model in R (lmer function from the lme4 package; the model has a complex random-effects structure). The interaction consists of two continuous variables and one categorical variable (two experimental...
13. ### Reporting a significant interaction

Hi! I am struggling on how to report a significant categorical x continuous interaction, which I found using a negative binomial regression. I have posted the output from STATA below. So far, I have said something along the lines of, "there was a significant lang2 by emotdys3 interaction term...
14. ### One significant interaction out of many

So I am in the process of interpreting a set of results. I conducted 6 regression analyses to determine if a variable acts as a moderator. One of the 6 interaction terms was significant. Should I attempt to rationalise this in terms of theory, or should I argue that the hypotheses were not met...
15. ### Which statistical model to choose?

Hey guys, I have a few hypotheses in a randomized control trial that I would like to test: 1) Effect of a treatment on several outcome variables (some of them are continuous, some of them are dichotomous) 2) Moderating effect of commitment in the treatment on effect 1) - Commitment...
16. ### Interaction effect

Hey guys, I would like to investigate effect of a treatment in randomized control trial. Also, I would like to investigate the moderating effect of motivation (of the participants who are included in the treatment group). I wanted to use a multiple linear regression with an interaction...
17. ### Generalized Linear Model: help interpeting interaction

Hello! I apologise in advance if I missed it, but I couldn't find an answer in previous threads. I run a generalized linear model with 1 factor (gender) and 5 covariates. No single variable appears to have a predictive value on my VD. However, when I test for interactions, many seem to...
18. ### Help interpreting an interaction in Binary Logistic Regression

Firstly, thank you for taking the time to read my problem that I am having. The goal: interpret the direction of the interaction term. Variables: I have two continuous predictors (heart rate [HR] and pupil dilatation [PD]), predicting a dichotomous outcome (diagnosis of conduct disorder -...
19. ### Interpretation interaction term in glmer()

Hi, I am using the glmer() function from the package lme4 for a mixed logistic regression model. Here, the formula is Y ~ X + Z + X:Z, where Y is the binomial outcome, X is a categorical predictor with 3 levels (X1, X2, X3, where X1 is the baseline), and Z is a continuous predictor. In the...
20. ### Interpretation of continuous interaction term

Hi all, I have a question regarding the interpretation of a squared interaction term in the following model: Y=β0+β1X+ β1X^2 + β2Z+ β3 X^2Z X and Z are continuous and X is negatively related to Y whereas Z is positively related to Y. Is it true that a negative interaction...