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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34 views

Dummy as moderator in regression analysis

I am working on data about the food industry, where companies should be divided according to their region (Asia, Europe, and North America) via dummies. This is supposed to be the moderator variable. ...
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1answer
39 views

Clustering and interactions in a multilevel model in R

We are conducting an individual participant level meta-analysis on a series of clustered randomised controlled trials, where we are mainly interested in an interaction effect with a characteristic (...
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0answers
10 views

Implications of adding extra “control” conditions to an ANOVA?

I'm planning a 2x3 ANOVA, all between subjects. I'm expecting a weak main effect for A...a main effect for B where one condition is different than the other two...and then an interaction effect where ...
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17 views

Problems with singularity and a cross-level interaction

I have the following data structure: 200 Participants each saw 32 visual stimuli. These stimuli were manipulated on two properties (level-1 predictors). The participants came from two different ...
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2answers
284 views

Argument on Interactions in The Book of Why

There is a paragraph on interactions in The Book of Why (Pearl & Mackenzie, 2018), Chapter 9 (I cannot share the page number because I have the book in epub format), where the authors argue that: ...
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1answer
115 views

Problems from having too many interactions in a regression?

Excluding the 'dummy variable trap', are the problems from including too many interaction terms in a regression any different from the problems of including too many continuous or binary variables in ...
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25 views

Interactions: mean centering, standardizing and standardized coefficients (betas)

I mean-center my independent and moderator variable before calculating the interaction term to avoid multicollinearity. In my regression output table, I subsequently report the standardized ...
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2answers
155 views

Propensity scores in logistic regression models

I have a query after reading a paper, which is about the effectiveness of a medical device. In summary, what the authors did was 1. Generating a propensity score using a multivariable logistic ...
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1answer
104 views

Advantage of the Gail-Simon Test (qualitative/ crossover interaction test)

It is common to use a product of two variables to test whether an interaction is present. In regression analysis, for example, we can include both main effects and the interaction and see whether the ...
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19 views

predicted probabilities - interaction plot

My regression analysis (run with GAM model as suggested by a statistician) showed a significant result between two dummy variables (SPRACHE ("Language" either german or french) and LERNERGRUPPE ("...
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1answer
29 views

Multiple regression interaction - test simple slopes

I measured participants' ratings on how they felt after perceiving an individually recalled event on a scale from -10 (very negative) to +10 (very positive) at two time points, t1: directly when the ...
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0answers
20 views

How to compute and interpret interaction term between continuous variables that have negative values?

I was wondering about the computation and interpretation of interaction terms of continuous variables that are used in a multiple regression. Normally, one would mean-center (or z-standardize) the two ...
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41 views

Interaction between 3 categorical variables - one with multiple levels

I am looking at how a continuous variable is affected by 3 categorical variables specifically if there are any interactions between two of them or all three of them (Yes I understand there are post ...
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41 views

How do I interpret interaction effects in a log-level regression model?

My model: log(y)=β0 + β1x1 + β2log(x2) + β3x1log(x2). The X1 variable is endogenous and I instrument it with a Z variable. Values of X1 are standardized to be between 0 and 1, where 1 is the highest ...
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14 views

Interpreting a hazard ratio for time-dependent coefficients

I have a cox model with two main effects (x,y) and two interaction terms (xt, yt) where t is time. I am having some trouble interpreting the hazard ratios. Does the hazard ration become more of an ...
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1answer
28 views

Interpreting coefficients in a regression model for a two-level categorical IV [closed]

I'm running a moderated mediation analysis in SPSS. However, I face some difficulties interpreting the results. I have one independent variable which has two levels (emotional and rational). Since I ...
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29 views

Is it possible to modelize an effect in one group only with an interaction term?

I'm studying all-cause cancer incidence in a large population. Since it is an important confounding factor for many cancers, I'd like to adjust for hormonal contraception and hormone replacement ...
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24 views

When to use an interaction with dummy variables, and when to estimate separate regressions? [duplicate]

I am interested in exploring heterogeneous treatment effects by category. As a simple example, imagine that I'm trying to predict the impact of job training on income in New York, and I want to ...
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1answer
43 views

Adding a 2nd interaction term makes 1st interaction term and the 2nd interaction term insignificant

I'm running a multiple linear OLS regression (X => Y) on a sample with 125 cases. My regression has two moderator variables (Z and W). Z and W correlate at about .4 but Z and W are two distinct/...
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1answer
137 views

Moderation analysis with non-significant main effects but significant interaction

I am doing a simple moderation analysis with one independent variable (IV), one moderator (M) and one dependent variable (DV). Results indicate that a regression model containing both main effects (...
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1answer
52 views

Which emmeans to choose between full and main effect mixed effect models with heteroscedasticity corrected

I have a split splot full factorial design : 3 blocks, each block contains 4 plots for factor E and each plot is divided into 3 subplots for factor F. I use a mixed effect model with random effects on ...
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8 views

What is an appropriate technique for large number of correlated predictor variables with interactions?

I want to allow the effects of a large number of continuous predictor variables to be different depending on which treatment group the individual is a part of. If I had only three continuous ...
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2answers
58 views

How to code effect modifier in a Cox Regression using R?

The definition of the distinction between the effect modifier and interaction term is: Interaction and effect modification are formally defined within the counterfactual framework. Interaction is ...
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1answer
35 views

Interpreting dummy variable interaction terms

I am attempting to model monthly retail electricity sales. To account for both the effects of seasonality and weather, I created an interaction term by multiplying 12 monthly dummy variables by the ...
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42 views

Interactions terms and the dummy variables

I am attempting to model monthly retail electricity sales. To account for both the effects of seasonality and weather, I created an interaction term by multiplying 12 monthly dummy variables by the ...
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1answer
43 views

When non-significant interaction effects make a significant main effect non-significant [duplicate]

Suppose that I have two IVs (AnxietyLevel & experimental conditions (dummy coded as 0 and 1), and two control variables (Age & Gender) and one DV (mean score on a questionnaire). And I am ...
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1answer
185 views

How to include an interaction with a quadratic term? [closed]

I want to predict $y$ with $x_{1}$ and $x_{2}$ and I suppose that $x_{2}$ has a quadratic effect on $y$ and that there is an interaction. How to model that? I've look in previous questions but there ...
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40 views

Longitudinal mixed-model with co-varaites

I'm currently have a longitudinal dataset with dependent variable Y measures over two time points (variable = Time) across 4 groups (variable = Group). This variable Y is a continuous variable ...
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71 views

simr power simulation testing interaction term for 2 factors

I have a model with two factors: a (4 levels) and b (3 levels). Each participant receives two problems (id as a random effect). I want to estimate sample size based on pilot data to give me ...
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1answer
33 views

Dummy code interaction among categorical variables [closed]

Do you know if there is a way of dummy coding the interactions among three independent categorical variables using SPSS? (with two levels each)
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1answer
34 views

How do you use panel data to isolate the relationship of interest for a particular individual within your panel?

I have a panel data set where Canadian provinces are the individuals. (I have annual data from 1997-2017). I am using a random effects model to see the impact of an explanatory variable $X_{it}$ on ...
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1answer
57 views

help interpret interaction effect in linear mixed effect

I am trying to predict response time (transformed in Log) from Group (a factor with two levels: NS and NNS), and Time of Testing (a factor with three levels: Pretest, Posttest, Delayed-test), using ...
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1answer
32 views

Interpret contradicting output of lmer model with categorical interaction in R

I am struggling to interpret my output in R. It does not make sense to me. I first regressed participants' ratings (= value) on manipulations (...
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0answers
71 views

Calculate odds ratios and P-value for interaction across multiple separate subgroups

I'm trying to understand/replicate an adjusted logistic regression analysis where a treatment effect is estimated separately in a number (>2) of subgroups and estimating an overall P-value for ...
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1answer
37 views

How powerful are second order interactions?

A lot of applications in statistics and machine learning model a phenomenon by second order interactions of variables and get good results. By second order interactions I mean, for a general variable $...
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2answers
93 views

Bayes factors and predictive accuracy in model comparison in rstan / brms

Despite reading up on the subject, I can't wrap my head round it, so the question remains on shaky grounds, and responses along the lines of "read chapter x" are very welcome. What I'm doing is I'm ...
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16 views

similar risk estimates between groups but have significant interaction

I am running a cox proportional hazard model to analyze the association between air pollution and risk of mortality. In the subgroup analysis, I obtained some confusing results. For example, when ...
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1answer
56 views

Visualize cross over interaction logistic regression categorical variable in R

I have performed a logistic regression with the following variables: X: Categorical with three levels (St, An, Int) M: Moderator, which has two levels (Mob,Desk) Y: Dichotomous dependent variable (0/...
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27 views

ANCOVA: resolving hetrogeneity of regression slopes with multilevel modelling vs adding an interaction term

On the Wikipedia page for Multilevel model it is written that [M]ultilevel models can be used as an alternative to ANCOVA, where scores on the dependent variable are adjusted for covariates (e.g....
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14 views

Estimating weights in the assignment problem

How would you learn a function with the emphasis on feature interactions? I have the standard assignment problem: $$ \max_{x_{ij}} \sum_{(i, j)} w_{ij} x_{ij}, $$ where $w_{ij}$ is the weight of ...
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35 views

Testing interaction terms individually and simultaneously

I am currently testing two interaction terms individually in OLS regressions. Both interaction terms are significant (p < .5) when tested individually (i.e., two regression equations, one for each ...
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12 views

non homogonous data and interaction

I have an experiment design with: Variable 1 - 2 levels Variable 2 - 3 levels And demographic information collected about my participants: Demographic 1 - 2 levels Demographic 2 - 3 levels ...
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18 views

Multiple linear regression with dependent as a dummy predictor

I have a model $Y = \alpha + \beta_1X_1 + \beta_2X_2$. $Y$ has a bimodal normal(ish) distribution, so I'm looking to see if the relationship between the predictors and the response is different for ...
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1answer
90 views

Help in Two-way ANOVA with Significant Interaction

(note: I removed the original table because there were some mistakes in it. I preferred to use R annotation of Sal's answer.) Hi everybody, I got the following results for an experiment of ...
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1answer
67 views

Can I use a t-test to follow-up on a non-significant interaction in an ANCOVA?

I have an experiment that compares the impacts on students' learning (as measured by their performance on a pre and posttest) of two versions of a classroom intervention: D and R. I did an ANCOVA ...
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16 views

Logit model: Interpretation of interaction effect with only dummies

I have a large binary logit model (cross-section) with many variables, mostly dummies. From the information on age, I have created 6 dummies: 17-24, 25-34, 35-44, 45-54 (reference group), 55-64 and 65+...
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0answers
20 views

How to properly represent a sum of interactions in ANOVA?

I would like to include an ANOVA-style linear model in my work that shows the main effects but has interactions lumped together in one term for brevity. When I do the analysis I will include the ...
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9 views

Interaction in logit

I am estimating a model where interaction terms play a role, and I am wondering which specification I should use, and how to interpret the results. More specifically, I regress a binary variable, say ...
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1answer
40 views

Interaction term to deal with heteroscedasticity

The variance in my dependent variable changes with a changing value in an important independent variable and is hence probably distorting the measured effect of the treatment. Can I combat this form ...
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0answers
15 views

Interpreting models with omitted interaction effects

Suppose I have two regressors, task availability (Xa) and task participation (Xp), and a DV Y. One can only participate in a task if it is available, but one can choose not to participate even if a ...