Questions tagged [interaction]

A situation where the effect of an explanatory variable may depend on the value of another explanatory variable.

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Beta coefficients from stratified analysis when there are covariates?

Suppose I have a regression model shown below Model 1: $$Y = \beta_0^\ + \beta_1SEX\ + \beta_2ALCOHOL\ + \beta_3SEX*ALCOHOL\$$ The predictors I am interested in are SEX (binary: 0 female, 1 male) ...
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Interpreting multiple regression coefficients with 2 continuous variables interacting and 2 categorical variables interacting

I find it challenging to interpret interaction effects in OLS multiple regression where the interactions are between two categorical variables and between two continuous variables. Say for instance ...
6k views

Intuition behind tensor product interactions in GAMs (MGCV package in R)

Generalized additive models are those where $$y = \alpha + f_1(x_1) + f_2(x_2) + e_i$$ for example. the functions are smooth, and to be estimated. Usually by penalized splines. MGCV is a package ...
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Effect sizes from LMM

My question is, how to get effect sizes for a linear mixed model? I am using the following model in SPSS: ...
395 views

continous moderator in a within subject design

I'm a first year PhD student and I am a bit at a loss regarding which test to use, and how to calculate power for a grant proposal. Any help will be much appreciated! I'm running all my participants ...
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What are the statistical assumptions, prior to running hierarchical regression to test interaction effects?

What are the assumptions that need to be met when using hierarchical regression, and subsequently simple slopes analysis to test and probe interaction effects and how can I test for them in SPSS? I ...
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Testing Independent variables impact during different decades

I am trying to test the impact that independent variables, Growth, Inflation, and Z (good economy for several quarters), have on the presidential vote received by the incumbent party. My alternative ...
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ANCOVA and its disturbing assumptions

It is possible to test for interaction in Analysis of Covariance (ANCOVA) between the independent variable and the co-variate, but isn't “the homogeneity of regression slopes” an assumption that ...
494 views

Can the Johnson-Neyman moderation interaction technique be used with a categorical moderator?

Can the Johnson-Neyman moderation interaction technique be used with a categorical moderator (3 categories)? 60%, 80% and 100%. I am guessing that it could approximate the interaction effect at ...
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Interact categorical variables in GLM in R

I am trying to predict child nutrition (binary) using a set of variables. The two that I want to interact are maternal education (none, primary, middle, HS) and wealth quintile (1,2,3,4,5). Thus far ...
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Interpretation of very small GEE Interactions

I have multiple GEE models predicting learning scores from the interactions of psychophysiological data of subjects, e.g. features of Electroencephalograph (EEG), respiration, etc., in a 2 condition ...
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Meta-analysis in R of pre-post treatment design studies

I would like to conduct a meta-analysis in R of studies using a pre-post treatment design. In every individual study 4 different subgroups of patients have undergone a pharmacological treatment and ...
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Interpreting coefficients of an interaction between categorical and continuous variable

I have a question about the interpretation of the coefficients of an interaction between continuous and categorical variable. here is my model: ...
302 views

Why does a positive average squared cross-partial derivative indicate an interaction?

I am studying Gradient Boosted Regression Trees and am looking at the H-statistic described on pages 18-22 of Predictive Learning via Rule Ensembles (2008). In the paper Dr. Friedman states: ...
510 views

How to detect interactions in a random forest model? [duplicate]

When I fit a regression tree model in R, I can somehow look at the plotted tree to figure out the interactions of the predictors. However, when I fit a random forest model, I cannot plot a tree ...
995 views

How do you assess a three-way interaction in a generalized multi-level model?

I am unsure which statistical tests I should use in order to follow-up my three-way interaction. I used to split my file and run the analysis twice per group, but as I read in the paper by Hayes & ...
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How to deal with differences in subgroup analysis but no significant interaction?

In case of a multiple linear regression I found a significant effect in a subgroup analysis (sample restricted to males). In the subgroup analysis restricted to females there is no effect. However in ...
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Repeated measures interaction betwen SNP and treatment with R

This is my first question is this forum. I have the a problem that I want to solve with the lme function of the nlme package of <...
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How to control for common method bias?

I am doing CFA to test for common method bias using an unmeasured latent construct method. The average common variance I am getting from the common factor is about 31% which is high (as should be less ...
622 views

Correlation and coefficients in ols

I am trying to fit a simple linear model with OLS. I have say 4 terms and the number of data points is >> 4, so no explicit overfitting. ...
768 views

Unfold degrees of freedom of interaction in factorial design analysis in R

I've been trying to analyse data from a factorial design with missing cells without much success until now. I'm using Anova from car package, that, according with I've read, can handle unbalanced data ...
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How to examine interactions between factor and covariate in a mixed effects model?

I have 2 factors A and B (5×3) and one covariate X in a within subject design. Here's ...
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Meaning of p-values for an interaction between a categorical variable (w/ >2 cats) & continuous variable

I have a question about the meaning of the p-values when testing an interaction between a continuous and a categorical variable (with more than 2 categories). When I do that in a glm model using R, I ...
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Small Sample, Low Baseline in DV, Interaction anyway?

Please assume that I have two metric independent variables (e.g., two blood parameters), and a dependent variable (e.g., a disease). On the DV, 0 represents the absence from the disease, 1 represents ...
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Is it possible to have a variable that acts as both an effect modifier and a confounder?

Is it possible to have a variable that acts as both an effect (measurement) modifier and a confounder for a given pair of risk-outcome associations? I'm still a little unsure of the distinction. I've ...
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Interaction Suppresses Main Effects in Repeated Measures GLM? [duplicate]

Possible Duplicate: What if interaction wipes out my direct effects in regression? I have three hypotheses within my experiment, and interpreting the interaction in relation to the rest of the ...
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Interpretation for simple slope analysis for curvilinear regression with interaction effects

When regressing income ($Y$) on age ($X$) moderated by gender ($Z$), I not only find significant effects for age ($X$), age squared ($X^2$), gender ($Z$), the interaction of age and gender ($XZ$), and ...
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Continuous-by-continuous interaction using simple slopes when I have nuisance variables in my model

I've created a multiple regression predicting 1 DV from 4 IVs (all mean-centered) + 1 interaction term between two of the IVs. The interaction term is significant. I'd like to get a nifty graph ...
231 views

How can I change the scores to make interaction effect in two way ANOVA significant?

My question is how to make an interaction effect become significant in two-way ANOVA. If my main effect A has an F value of F(1,80)=25.5 for example, and my main effect B has an F value of F(3,80)=15,...
382 views

To exclude a main effect that is not of interest in ANCOVA, or not? [duplicate]

Possible Duplicate: Including the interaction but not the main effects in a model I have an experimental design with pretest and posttest. Two groups, experimental and control group. I am ...
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How to quantify moderation effect in an intervention study with multiple time points?

I want to measure a moderation effect between 3 continuous variable in an intervention study. I am using scores from self-report measures of masculinity, emotionality, and psychological distress. The ...
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Repeated measures ANOVA within and between factors

I have conducted repeated measures ANOVA, with 2 factors: One within factor (time, pre-post intervention) and one between factor (...
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Calculate standard errors: interaction between 2 factors, one of which has 3 levels in a regression model

I have the following model: $y \sim b_0 + b_1x_1 + b_2x_2 + b_3x_1x_2$. $x_1$ is a factor with 2 levels (0 and 1), and $x_2$ is a factor with 3 levels. I know that to calculate standard errors for ...