# Questions tagged [interaction]

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

594 questions
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### Ratios in Regression, aka Questions on Kronmal

Recently, randomly browsing questions triggered a memory of on off-hand comment from one of my professors a few years back warning about the usage of ratios in regression models. So I started reading ...
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### Interpretation of crossed random effect interactions in lme4

I'm considering a model in lme4 in which I am estimating random effects for two crossed factors, very similar to the Machines example in Bates' 2010 draft book (http://lme4.r-forge.r-project.org/lMMwR/...
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### Panel regressions with an interaction term between a time dummy variable and a time invariant variable

I have estimated the coefficients of the following equation, using the fixed-effect model: $Y_{it}=\alpha _i+ \rho _t + \beta _1 X_{it}+\beta _2 C_i*D_t+\epsilon_{it}$ I have observations from 1980 ...
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### When and How to Scale Numeric Interaction Variables in Machine Learning Model

I found one similar question on cross validated, but it was unanswered; my apologies if this has been answered. I'm experimenting with feature interaction in a regression model I'm working on in R. ...
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### Interaction plot between categorical and quadratic continuous variable

I ran a GLMM model with a binomial response to analyse bear presence at feeding sites (0 = absent, 1 = present) within two years. My code is: ...
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### Cox interactions and co-linearity

I am interested in developing a model to predict survival based on a few predictors: age, sex, and two lab values, albumin and globulin. I have approximately 14,000 deaths in the data. I initially ...
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### Testing differences between slopes by examining proportions rather than interactions

In a recent article published in Nature Genetics, Francioli et al. argue that the relationship between paternal age and mutation rate depends on what part of the genome you're looking at (intergenic ...
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### When including a linear interaction between two continuous predictors, should one generally also include quadratic predictors?

Suppose I am fitting a linear model, and I have two continuous predictors x1 and x2. I think that they might interact, so I add ...
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### How to write a mathematical equation for GLM model with gamma and gaussian distribution?

I am writing a paper and the following is a code that I wrote in R. The reason that I am struggling with this is because I tried hundreds of models with different variables and the following model ...
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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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### How to interpret a two-way interaction in a 3-way interaction model

I am trying to predict y with variables a, b and c. I have two models and I get different results depending on how I fit my model. Model A is the simpler model, in which I exclude variable c. In ...
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### Forms of interaction between variables Random Forests take into account

What forms of interaction do Random Forests take into account? I understand from other posts ( Including Interaction Terms in Random Forest ) that Random Forests take into account interactions like x1 ...
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### Incorporating Measurements of Item Uncertainty into Bayesian Models

Imagine I have a dataset of four variables: Age (Continuous) Gender (M/F) Vote for Incumbent (Yes/No) Like Leader (Yes/No) However, I also have two additional pieces of paradata: how long it took ...
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### A few questions regarding the practice of heterogeneous treatment effect analysis (a.k.a, interaction detection or subgroup analysis) methods

Imagine I am looking at a randomized experiment between a control and one or more treatment conditions. For example, I have a treatment that aims to get people out of debt. I randomize people to ...
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### Could interaction effects prevent GLMM's (lme4) from converging?

In the following analysis, I am exploring the association between health outcomes and a range of environmental and socioeconomic predictors. These data have been collected from 9 countries, over ...
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### Framework for simulating SEM data w/ moderation + mediation, testing models

I'm interested in extrapolating treatment effects from RCTs to new populations under conditions where populations exhibit relevant differences that induce differences in treatment effects. My aim is ...
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### Interaction effect in random forest

I'm interested in interaction effect between variables in random forest. I found some information here https://www.stat.berkeley.edu/~breiman/RandomForests/cc_home.htm#workings. The operating ...
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### Can a random slope be interpreted similarly to interaction effects in longitudinal analysis?

I am modeling wheat yields over time at several locations using mixed models in R (lmer function). My selected model is as follows: ...
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### Interaction terms in multinomial logit regression

I'm analyzing the relationship between women's BMI status (underweight, normal, overweight) and five predictors ( their wealth, their education, the region where they live, their score of dietary ...
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### What is the difference between bi-level linear models and models with interaction terms?

My question is triggered by this question. I can't see that it has been asked here before, even though it looks like a natural enough question. Suppose I have hierarchical data. The Wikipedia article ...
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### How to check variables changeable dependency in R?

I would be very thankful if somebody could help me and explain the answer in simple terms. I have y, x, z variables. They are countinuous, no missing values. y is dependent variable, x and z ...
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### How does the presence of factors affect the interpretation of the other coefficients in a regression?

The answer to Interpreting coefficients of an interaction between categorical and continuous variable contains a phrase that seems to have some significant impact on how coefficients are interpreted ...
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### How to determine the significance of an interaction?

My question is simple: How do you determine the overall significance of an interaction (i.e. the marginal effect of $X$ on $Y$ for different values of $Z$)? But the background is a bit long-winded,...
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### Which statistical test for women height?

Suppose women may have Blue or Red eyes. We make a first cheap research on a 100 women checking just one eye of each woman. So after the research we have results: At least one eye Blue have avg ...
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201 views

### Contradicting interaction significance with graphical visualisation in glmer

I'm investigating environmental effects (wind) on acoustic receiver detection probability for two types of transmitters using a binomial glmer. While my model analysis indicates that there's a ...
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### Estimating a confidence interval around the average of an interacted treatment effect

I've got a causal inference situation with heterogeneous treatment effects. In addition to simply estimating coefficients, I'd like to get an average effect of the treatment at the covariate values ...
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### Standard error computation with interaction term

I aimed at studying the effects of an exposure (E) on fetal growth estimated by repeated ultrasound measurements (n = 2 measures per participant in the following example). I used interaction terms of ...
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### Effect of Age-Period-Cohort on prediction and interactions

I am performing a longitudinal analysis and I am curious if the predictors we are including in the model will introduce any unexpected effects. We have subjects with multiple points of follow-up ...
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2k views

### How to interpret chi-squared test for main effect in presence of interaction term

I have run a sequence of nested multi-level models using lmer, and looked at both the summary output giving all the coefficients, etc, as well as the Anova output which does a chi-squared test on each ...
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### Power analysis for moderator effect and mediation analysis

I want to do an a priori analysis of minimum sample size with G*Power and I have two questions about this: First, I will test an interaction effect for a moderator variable. I am not sure which ...
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### How to deal with kurtotic interaction variable?

I'm going to do a multiple regression analysis with two continuous IVs and their interaction. I've centered the IVs and then multiplied one with another for interaction. My problem is that the ...
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645 views

### Interpretation of interaction term in Cox PH model when centering LP on mean values of predictors

Let's say I have a Cox PH model for predicting the risk of dying, that in a simplified form looks something like this: ...
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### Fractional Polynomial interpreting interaction terms

Background: I have developed a logistic regression model where I am trying to analyze the effect of socio-economic data of a family on their probability of receiving a home loan. I have used ...
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### Algorithm for selecting interactions without very many degrees of freedom (mgcv, gam)

I've got a semi-parametric model that I'm fitting with GAM's (mgcv in R). It is of the form $$y = \theta + X'\beta + f(Z) + \text{Interactions!} + \epsilon$$ I've got 289 observations. Many of ...
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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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750 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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361 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,...
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### Using a t-test to follow-up on a non-significant interaction in an ANCOVA?

My question is about whether a t-test can be used to follow-up on a non-significant interaction found with an ANCOVA. I have an experiment that compares the impacts on students' learning (as measured ...
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### Interpreting interaction term on highly correlated variables

Somebody at a meeting today made the following comment about a Marketing Mix Model (Linear Regression) we run every year. We should account for the high collinearity of the two Marketing Variables (...
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### Comparing two difference-in-difference models when making the treatment group larger

I have a question regarding some potentially existing empirical tests in the difference-in-difference context. Assume that I have the usual setting of observing some hypothetical outcome for a ...
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### What is the best way to choose interactions between continuous variables for Logistic Regression?

I have a logistic regression model that I am working on for a school project. I have about 55 predictors, all of which are continuous. I am relatively new to the idea of "interactions" between ...
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### How to do simple slope analysis for interactions in zero-inflated negative binomial regression in r?

I used the function 'zeroinfl' from the 'pscl' package to fit a zero-inflated model with negative binomial distribution (zinb). Results show significant interaction effects and I should do simple ...
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### How to Interpret Co-Linear Interaction Term?

I am looking to model transit ridership based on demographics at the stop level. For each stop, I know: ONS: Total boardings per day - averaged over the number of times a bus pulls up at the stop ...
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### Is a three-level multilevel model appropriate for my research question?

For a study that is currently in the planning stage we are considering what kind of model would be most appropriate. We are interested in the interactive effect of a drug (vs. placebo) and hormone ...
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### perfect separation after adding interaction term

I am using glm to estimate a model (dependent is dummy). I have two continuous variables that I want to test their interaction. As soon as I add the interaction ...
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### Linear mixed model: Setting custom contrasts for interactions and main effects with glht in R

I am currently learning statistics with R, and I am a bit confused about how to set custom contrasts for interaction effects. I tried removing the intercept from my model: ...
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### Refitting the ANOVA model

I have performed a Two way ANOVA,for one response and two categorical variables. I had found that EDA with a plot of means shows that there might be an interaction between my categorical varibles ...
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### Test significance using Type II ANOVA following Type III ANOVA?

I hope you can help me with a theoretical question about how to proceed in my analysis. I have come across many posts discussing differences between Type II and III SS Anovas, however, because I don't ...
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### Endogenous interaction terms as IV

I want to estimate $$y_i=\beta_0+\beta_1 X_{i1}*X_{i2}+\beta_2 X_{i1}+\beta_3 X_{i2}....+\epsilon_i$$ where $X_{i1}*X_{i2}$: the instrument variable of what I want to estimate, continuous $X_{i1}$: ...
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### What variant of interaction when the PH assumption is violated in a CoxPH Model?

When the assumption of proportional hazards is violated, the suggestion is to interact offending covariates with time (or a function of time). In this blog post, the author suggests to include only ...