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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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significant Interaction between a significant discrete variable and non significant continuous variable

In my dataset, I have to test the effect of humidity on the height of plants. However, we have an extra effect which is nitrate on height. Each plant had a nitrate measurement but we had one group in "...
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Resampling-based Confidence Intervals for Relative Excess Risk Due to Interaction

Relative Excess Risk Due to Interaction (RERI) has been used to quantify the joint effects of 2 exposures in epidemiology. RERI is the proportion of disease among those with both exposures that is ...
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Regression with interaction, interpretating main effect

I have a question regarding testing interaction terms in regression. When we have significant interaction term, do we still interpret main effects? I have made two models, one with interaction term ...
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28 views

Can you “reverse” an interaction plot and still interpret it?

I am interested in studying the interaction with a ordinal predictor p and continuous moderator m on an outcome y with a simple model of: y ~ p + m + p*m However, since my predictor is categorical, ...
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If A causes B & A causes C, can B modify the effect of A on C?

Suppose I roll out an initiative to promote a new vaccine in a country, call this intervention A. A causes uptake of vaccines C, but it may or may not also cause backlash from community leaders ...
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In linear regression, why should we include quadratic terms when we are only interested in interaction terms?

Suppose I am interested in a linear regression model, for $$Y_i = \beta_0 + \beta_1x_1 + \beta_2x_2 + \beta_3x_1x_2$$, because I would like to see if an interaction between the two covariates have an ...
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Weird results in ANOVA: the three-way interaction has a pvalue of exactly 1

I am running a three way interaction, predicting 'judgment' from 'factor_1' (between subject, two levels), 'factor_2' (between subject, two levels) and factor_3 (within subject, two levels). I have ...
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Regression: Interactions terms of factors with several levels (interpretation)

I'm running the following linear model in R: lm(formula = Valence ~ StatusOfMandarin * Condition, data = d_afraid, na.action = na.omit) My data is as follow ...
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Interaction in fractional polynomial regression in R using the mfp package

I am modelling the relationship between waist circumference and triglycerides using fractional polynomials and the mfp package in R. I want to assess whether this relationship differs for ethnic ...
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1answer
42 views

Testing the significance of a main effect using model comparison, when an interaction is included

I am fitting a linear mixed effect model (using lmer), and want to obtain p-values via model comparison. As far as I understand it, the procedure is: (i) create a ...
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1answer
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ANOVA: do I interpret the significant main effects not involved in interactions?

My statistical model is Dependent ~ A * Sex + B * Sex. (i.e., Dependent ~ A + B + A:Sex + B:Sex). I have prior reason to expect ...
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Is there a collinearity issue when using: x, dummy indicating extreme negative value of x and their interaction?

I was wondering whether I can build my baseline model using the following variables without incurring in any multicollinearity issue: $X_1$= Net capital flows over GDP (which may be positive and ...
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SEM setup question: Dummy coding with interaction term

I have an SEM that fits well according to several metrics and returns meaningful results. However, I'm not sure if the structure is valid. I have 3 between subjects conditions (2 treatments and one ...
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52 views

Calculating Confidence Interval with log-transformation

I fitted a linear regression with a 3rd order interaction and adjustment for confounding variable which looks like this: $$ log(Y) = β_1S + β_2T + β_3M + β_4ST + β_5SM + β_6TM + β_7STM + β_XX $$ ...
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Logistic regression using a predictor with a spike at zero

I am modelling the effect of oxygen exposure in an intensive care setting on survival. This isn't straightforward from a biological perspective as there are many confounders, including a treatment ...
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Non-significant three way interaction but three significant two-way interactions

I am analyzing results of an experiment with the help of a 2 (Group) x 2 (positive or negative mood) x 3 (baseline vs after mood induction vs follow up) repeated measures anova. For one dependent ...
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Standardizing predictors creates dependcies between interaction term and main effect

who can solve this puzzle? I have predictors A (1,-1), B (count variable), C (1-5) A is not correlated with B or C The interaction term (BxC) is not correlated with A The interaction term based on ...
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32 views

Random Group By Time Interaction

Assume we have two groups of subjects which are measured repeatedly over time with respect to the values of a continuous outcome variable. To analyze the resulting data in R, we might fit a linear ...
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Need Help Interpreting Interaction Terms in Regression Analysis

I am analyzing an ad campaign that happened in Florida. I have data on 2 states. My model is as follows: Weekly Revenue = B0 + B1 * Florida Dummy + B2 * Time Period of the Ad Dummy + B3 * (Florida ...
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Interpreting contrasts for non-significant interaction in a linear mixed model

I am building a Linear Mixed Effects Model to investigate how activity levels (AL) change between two different types of therapies (TherapyA vs. TherapyB) and how different covariates influence the AL ...
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1answer
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Significant interaction effect for a subgroup but not overall

I fit a GEE model looking at the relationship between cognitive score and head impacts. Head impacts is a categorical variable separated into 4 quartiles by amount of exposure. Here are the results: ...
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1answer
259 views

Can you have interaction terms for both “sides” of a dummy variable in a single regression?

I'm really not sure how to phrase my question properly, so I apologize if this has been answered elsewhere. Let's say I'm interested in using a regression to predict wage using sex and an interaction ...
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Moderation Analysis in a 2×2 Pre-Post-Design

I have two groups and two measurements for each group (pre and post intervention) and I need to test the influence of a third continuous variable that I assume moderates this relationship. After doing ...
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Differences between Simple Effects, Pairwise Comparisons, and planned/post hoc comparisons?

I am very confused as to the differences between simple effects, pairwise comparisons, and planned/post hoc comparisons. From what I understand, after running an ANOVA, you would use one of these to ...
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Why does it not make sense to compute effects for lower-level interactions in the absence of higher-order interactions?

The documentation of effects package says "If asked, the effect function will compute effects for terms that have higher-order relatives in the model, ...
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two-way interaction only significant when including third factor

I have a mixed model similar to this: lmer(y ~ f1*f2 + (1|sub), data=dat) The f1*f2 interaction is not significant. However ...
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Interaction in a 2 by 2 factorial design

This is a little difficult to explain problem but here it is: I have a 2 by 2 Factorial study design: Say Factor 1 with level a and level b (both categorical); and Factor 2 with level c and d (both ...
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Plotting interaction of categorical predictor and continuous modifier

I fit a GEE model examining the interaction between my predictor: heading quartile (categorical- dummy coded) and a moderator variable: head circumference (continuous). I would like to visualize the ...
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Can I average my standard deviation across the levels of the main effects when computing the difference standard deviation for an interaction?

I am currently trying to perform a meta-analysis of an interaction effect between 2 factors (2x2 ANOVA). I am using the raw mean difference as my effect size, because the interaction effect size is ...
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Can polynomials, interaction variables, and autoregressive variables trigger exogeneity issues in regression?

I would think the introduction of the mentioned types of variables would introduce exogeneity issues in regression models. However, in such circumstances are these exogeneity issues material, or can ...
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P value for main effect of independent variable is changing when moderator is changed

I am trying to run a model 1using PROCESS within SPSS. I am running models with the same independent and dependent variables, and covariates, and changing only the moderator. Each time I change the ...
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Difference between tensor product and main effects plus interaction in mgcv [duplicate]

I was under the impression that using te and adding the main effects with s plus the interaction with ...
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1answer
30 views

Non-parametric tests for interaction effects

I have two datasets that are both organised as follows: an algorithm calculated a quality score (Q) of a specific image (image) that was processed using a certain algorithm (method). One has 315 ...
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1answer
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How do I specify an outcome variable (y) as count data using a poisson regression in a multilevel model?

I have three variables with multilevel data: Level 1 DV: deviant behaviour Level 1 IV: negative affect Level 2 IV: consideration of others (personality trait) Here is my model: ...
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1answer
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Problem understanding the interaction term of mixed effects model

I have a question regarding the meaning of an interaction term in a linear mixed effects model. Considering the following experiment (similar to a real one I have): there are three sites, each with ...
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Glmer - Changing refrence level changes data

I am currently fitting a glmer model to my data. Formula: (y ~ x1 * x2 * x3 + (1 | RandomEffect1) + (1 | RandomEffect2)) x1, <...
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1answer
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how do I plot interactions with continuous and categorical predictors in mixed models?

I'm very unsure how to plot mixed-level data consisting of a mixture of categorical and continuous predictors, so any help would be appreciated. This is the data ...
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Log-transformed DV and coefficient of interaction term

I am having difficulty interpreting the significance of positive tone (measured as percentage of words in a sentence that are positive in tone) for females and males. The following is the regression ...
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GLM - interacting predictors for which the mediator only applies to one type of outcome

I am running a simple GLM with an interaction of the two main predictors. The outcome (dependent) variable is binary and takes the value of 1 when the product is ...
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Interaction between covariate and 2-level within-subjects factor is of research interest. How to test

I'm interested in interpreting the interaction between a continuous variable (C) with a dichotomous within-persons factor (A) on a continuous DV (DV). What is the best overall test of this? Would it ...
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Interpretation and practical significance based on multiple linear regression coefficients

I am having difficulty articulating the practical significance of positive and negative tone in job application cover letters for male and female job candidates. I obtained the following linear ...
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Different significance in GLMM interactions

I am confused about different significance results obtained in GLMM's. First, my set of relevant variables: ...
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Accounting for Interaction between Independent variables

Is there some trustworthy resource on effect of interactions if not accounted for. Especially the situation is often, let's assume heart surgery, age, gender and logistic euroscore(derived from age ...
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1answer
53 views

GAM interaction- how to interpret

I am working with a GAM model (based on a negative binomial distribution): model_n = gam(y ~ x1 +x2+ x3+x4 + s(x5)+x6+s(acc, by=ses)+x7+x8+ x9+x10, data=totalfinals, family=negbin(3)...
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Categorical variable interaction compared to individual regressions

We are examining our understanding of interaction terms in categorical variables. We have a three category variable, and the model is: $y=\alpha+\beta x+\beta_0x_0+\beta_1x_1+\beta_2xx_0+\beta_3xx_1$ ...
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63 views

2SLS IV with endogenous interaction in Stata: Difference between ivreg2 and manual estimates

I want to estimate 2SLS in Stata with two endogenous, continuous variables: $X_1$ and the interaction term $X_1*X_2$. The other IVs $X_2...X_N$, including the quadratic $X_2^2$, are all exogenous. I ...
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1answer
20 views

Two-way interaction term and simple slope

In my study, I am looking at gender interaction with an independent variable. In the fitted linear regression, if the gender*var1...
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1answer
34 views

How to properly test simple effects: factor recode or data subsetting

I have seen people test their simple effects in two different ways and would like to know which is the correct one and why. The two methods are briefly explained below: recoding method: Involves ...
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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 ...