Questions tagged [interaction]

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

Filter by
Sorted by
Tagged with
3
votes
2answers
1k views

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) ...
4
votes
1answer
5k views

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 ...
30
votes
1answer
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 ...
2
votes
0answers
1k views

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: ...
0
votes
0answers
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 ...
3
votes
1answer
4k views

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 ...
0
votes
1answer
77 views

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 ...
6
votes
2answers
5k views

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 ...
1
vote
0answers
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 ...
3
votes
1answer
19k views

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 ...
1
vote
0answers
753 views

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 ...
2
votes
1answer
874 views

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 ...
2
votes
1answer
193 views

Fitting ratios in multiple regression formula

I would like to ask a (probably very simple) question with regards to multiple linear regression. I have an experimental formula in the form: $$ Y \sim \frac{a_0 \cdot X_0}{(a_1 \cdot X1) * (a_2 \...
5
votes
1answer
2k views

Interpreting interaction effects in a multilevel model

I conducted a multilevel analysis using repeated measures across four time points. The model contains intercept, linear slope and quadratic slope. I am interested in examining the extent to which ...
3
votes
1answer
813 views

OLS Regression: Interaction effect is significant by itself, not when included in full model--ok to report?

I have a sample with 400 cases. When I run my full model, which includes 13 predictors, the interaction term is non-significant. However, when I run a model only including the three variables involved ...
7
votes
1answer
4k views

How do I create and interpret an interaction plot in ggplot2?

I am trying to make an interaction plot for this set of data, but I want to make it with ggplot2. I am trying to predict VP using the predictors G and P, (these are columns in the dataset which I have ...
1
vote
0answers
411 views

Difference between p values of interaction

I was wondering which p-value to use when i am testing the significance of an interaction between two continuous variables. Here is my model with the interaction: Coefficients: ...
0
votes
0answers
2k views

Is it valid to include several interaction terms but exclude main effects because only interaction effects are significant? [duplicate]

I have a statistical problem in connection to interaction effects and main effects in the social sciences. I am doing a regression where I have two interaction terms with one common variable. The ...
2
votes
1answer
141 views

How to code values for males when they're only meaningful for females? [duplicate]

I'm building a predictive model for a medical condition that happens in both men and women. Physicians have reported that in some cases for women, their menstrual history seems to be a risk factor, ...
2
votes
2answers
3k views

How do I interpret the results from a basic interaction plot from the R effects package?

Using the method in this post, I have made a plot to visualize the interaction between two predictor variables using the effects package in r, but I'm not really sure what I am looking at. Tide ...
1
vote
1answer
109 views

illustrate interaction without ANOVA, other methods?

I am wondering whether there are acceptable ways to illustrate the presence of an interaction besides using an ANOVA. I can't use an ANOVA because I have unequal sample sizes, and due to the nature ...
1
vote
2answers
473 views

Interactions make terms significant in regression when they should not be

I am writing code to prepare for running a logistic regression on real data. I have sample data for all my IVs but not for the outcome variable. There are many strong dependencies among the IVs but I ...
12
votes
1answer
16k views

How to do an instrumental variables regression with an instrumented interaction term in Stata?

I'm having a bit of a problem with Stata syntax. I need to do the following regression: $$y = ax + bz + c(xz) + e$$ where both $x$ and $z$ are instrumented and also the interaction term $xz$ uses ...
1
vote
0answers
71 views

What test/method is suited for analysing and modeling answers from a survey?

People got a list of different documents and were asked if they find things important or not and if they think the documents would be easy to get or not. People belong to different groups and have ...
1
vote
0answers
351 views

Time consistency of interaction effect in GLM

I am thinking about how one should check for time consistency of in a GLM. Model: $$ \eta_{ijk} = \beta_{0} + \beta_{i}Year+\beta_{j}Var1+\beta_{k}Var2+\beta_{jk}(Var1 \times Var2) $$ If I were to ...
1
vote
2answers
1k views

Do I discuss the lack of interaction if I already discussed lack of main effects?

I conducted an experiment with 2 independent group variables (gender and language - language indicates either native speakers or 2nd language speakers) and ran a 2 way ANOVA. There were no main ...
0
votes
1answer
311 views

How do I interpret the results of a regression which involves interaction terms?

If I have a linear regression of the form: $$y \sim 1+\beta_1x_1 + \beta_2x_1x_2,$$ where $x_2$ is a Boolean variable depending on another variable $x_{2cont}$, a positive variable: $$x_2 = \begin{...
9
votes
1answer
16k views

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: ...
2
votes
1answer
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: ...
2
votes
0answers
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 ...
1
vote
0answers
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 & ...
3
votes
2answers
3k views

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 ...
3
votes
0answers
235 views

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 <...
2
votes
1answer
3k views

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 ...
2
votes
0answers
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. ...
3
votes
0answers
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 ...
8
votes
3answers
1k views

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 ...
7
votes
1answer
5k views

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 ...
2
votes
1answer
205 views

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 ...
10
votes
2answers
6k views

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 ...
0
votes
1answer
2k views

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 ...
2
votes
2answers
1k views

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 ...
1
vote
1answer
897 views

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 ...
-1
votes
1answer
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,...
2
votes
2answers
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 ...
4
votes
0answers
613 views

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 ...
3
votes
2answers
11k views

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 (...
4
votes
1answer
6k views

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 ...
1
vote
0answers
312 views

Changing reference level on mixed model changes pMCMC value

I'm using an lmer on a set of continuous data. This post helped me a great deal when interpreting results, as I have two conditions and three levels as well, but I've run into a frustrating problem. ...
3
votes
0answers
378 views

Binary interaction terms using lmer

I am trying to create a model using the lmer function. The model will contain the continuous response term "Average.profit" and explanatory terms "Type", "OtherType,...