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

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The difference between adding a main effect of Factor C, and also adding an interaction between Factor A and C into a regression model?

I have a logistic regression model with two dichotomous predictors: Factor A and Factor B. I found that there is a significant main effect of both Factor A and Factor B. Now suppose I want to see if ...
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13 views

permanova or non-parametric test for multiple explanatory variables and interaction

Hi I am trying to find a test to analyse the following data set. Response variable is failure or success (0 and 1) measured over 4 time points, under 2 different treatments (light and temperature) in ...
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12 views

How to incorporate characteristics of the object of outcome variables as predictors in model

I'm working with survey data for a social science research topic. The particulars aren't super important, so I'll use a simplified version to make it easier to understand what I'm trying to do. I say ...
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18 views

R square change for 2-way interaction model

I want to test a regression model with neuroticism as focal predictor, agreeableness as moderator and RT variability as dependent measure (covariates: attentional control and mean RT). Previously, I ...
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1answer
15 views

One main effect and one interaction in R using multiple regression, is that possible? And why am I getting two interaction terms in output?

I have two factors that are fully crossed, the levels of the factor are each coded 0 and 1. I am running a regression testing for one main effect and one interaction. The following is my logistic ...
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28 views

Why do we ignore the main effects when the interactions are not significant in a three-way ANOVA?

I'm following an SPSS guide online, and the procedure is to first test for a three-way interaction. In my case there was no sig. three-way interaction. Then the procedure asks me to consider two-way ...
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1answer
21 views

How to check if the correlation between two continous variables is influenced by a categorical factor?

I have a data frame (df) where I see correlation between two continuous variables (c1 and c2). I need to know whether the observed correlation between the two variables differs between groups, which ...
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31 views

Multivariate Mixed Model With Continuous Independent Variable - SPSS or R?

I've been trying to find an appropriate statistical technique to analyze multiple IVs and DVs with no luck. The IVs include 1 trichotomous within-subjects factor, 1 dichotomous between-subjects ...
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68 views

Computing R-squared change, F-, and p-values for the interaction / moderation term [closed]

I would like to compute R-squared change for the interaction/moderation term in a multiple regression model, along with the corresponding F- and p-values. Previously, I have worked with the modprobe ...
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14 views

Permutation to test SNP interactions

sampleID case/ctrl var1 var2 var3 var4 var5... sample1 0 1 0 0 1 0 1... sample2 1 0 0 0 0 1 0... sample3 0 1 1 1 0 0 0... sample4 1 0 0 0 0 1 0... ... case/ctrl status is binary, variant status is ...
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Mixed ANOVA interaction effect - How do I which treatment was more effective?

I have conducted a mixed between-within ANOVA with 3 intervention groups and 2 measurement times (pre/post) in SPSS. There was a significant Time*Group interaction, but significant main effects. How ...
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Interpreting an apparent inconsistency - fitting regression models on subsets suggested by an interaction

Say we learn a linear regression model with three continuous predictors $X_1$, $X_2$, and $X_3$ (along with interaction terms $X_1X_3$ and $X_2X_3$), for some variable Y. The fitted model suggests a ...
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31 views

How to calculate the effect size of differences in groups using dummies in multiple regression?

I am running a multiple regression analyses on a sample of 1800 respondents. The dependent variable is the mean of a 5-point likert scale and I have 6 predictors (antecedents) also using mean of ...
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10 views

Interpreting interaction between time and time-varying predictor in mixed models

I have measured the DV and predictor at 2 timepoints in a single group, and am using the MIXED procedure in SPSS. I want to see whether change in the DV over time is predicted by change in the ...
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What's the drawback of using interaction terms to analyze the pre-post control data?

I am trying to analyze the data with the pre-post-control design in the context of RNA-seq analysis. I have read Best practice when analyzing pre-post treatment-control designs, but I am still ...
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7 views

How to automatically add 2-way interaction terms in SAS proc hplogistic

I am trying to run a model using SAS proc hplogistic. The syntax I used is (this is just an example, the actual data set has 100 independent variable, so it's difficult to type all interaction terms ...
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34 views

Difference-in-differences model: do I have to include hierarchical terms with interaction term?

I am contemplating using a DiD model to see the effect of an intervention on population attitudes. My DVs of interest are ordinal (Likert-style) and binary. I have two agencies measured at two time ...
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17 views

How to interpret simple effect of a variable interacted with several others?

I am sure this has been asked before (similar here but no answer). But I have not found an answer yet. To give you a short frame: I am researching firm level data and I am ivestigating several ...
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1answer
28 views

Interpreting interactions when main effect is not significant

I just started fooling around with R and I am quite struggling with mixed models: I have the following experimental layout: Seven different viruses, including ctrl virus; 27 mice, randomly infected ...
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1answer
54 views

Representing interaction effects in directed acyclic graphs

Directed acyclic graphs (DAGs; e.g. Greenland, et al, 1999) are a part of a formalism of causal inference from the contrafactual interpretation of causality camp. In these graphs the presence of an ...
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1answer
60 views

Does it make sense to interact two continuous variables in econometrics?

Let's say I have three variables: Variable A, B and C, where C is the product of A and B. Both A and B are continuous variables. If I regress Y onto A and B, A is significant and B is not. Then, if ...
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Is it possible to use several interaction terms?

I came across this equation when I was reading the article: $$\textrm{Y} = \alpha + \textrm{X}_1 (\beta_0 + \beta_1 \textrm{X}_2 + \beta_2 \textrm{X}_3) + \varepsilon$$ At least, I can understand ...
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Testing the utility of adding a continuous variable to a nonlinear regression.

Let’s say I have the hypothesis that soil fertility affects the relationship between weed biomass and crop biomass. One way to go about testing that hypothesis might be to model the relationship ...
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27 views

Model change after switching reference level in R logistic regression model with interaction

I'm fairly new here so my apologies if I'm asking something obvious. My problem is the following: I have a dataset in which I want to examine the interaction of a risk-factor with an intervention to ...
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37 views

Question about fixed-effects/time-effects model in R/plm

I have a few questions about using the plm package's models to get fixed effects and time effects. Here's a basic sketch of the code: ...
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15 views

glmnet for Mixture Model

I have a distribution that looks like a Gaussian Mixtures And then I use Python's GMM Classification package to cluster them into clusters and then perform glmnet on each of the cluster. Is this ...
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1answer
47 views

R: interaction in model output

Let's say you're trying to fit a model to a dataset that includes categorical variables, group (A or B) and treatment (1, 2, 3 or 4). In R, your model formula would be DV ~ group * treatment (DV ...
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1answer
24 views

post hoc test for 3 way anova

I am doing ANOVA using three fixed independent factors of which one is sex (two levels 'male' and 'female'), temperature (three levels: 1,2,3) and quality (two levels: good and bad) and I want to see ...
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17 views

Tobit and Categorical Independent Variables

I am using Stata 13 to estimate a Tobit model with a endogenous variable which is bounded from above. My research is focused on firm level data. I have numerous moderators. Among these is a ...
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34 views

post hoc test for unequal sample size and variance

I have a data frame on which I am doing ANOVA using three fixed independent factors of which one is gender (two levels 'male' and 'female'), temperature (three levels: 1,2,3) and quality (two levels: ...
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1answer
22 views

Interaction effects and insignificant main effects - Back to basics

Imagine the following regression model: $\text{Abnormal Returns} = b0 + b1*SENT + b2*SIZE + b3*SENT*SIZE + e$ SENT is a standardized variable. SIZE is equal to 1 for "uncertain" firms, and 0 for ...
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3-way interaction with polynomials and 2 categorical variables in a LMER-model in r

My dataset contains the following variables: Within-Subject factor: Target After Onset Prime (4 levels) Within-Subject factor:Prime (2 levels; Categorical) Within-Subject factor:Target (2 levels; ...
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65 views

Clarification on calculating odds ratios for interaction between continuous variables

I know this or a similar question has been addressed more than once on CV, and I've tried to read/understand the responses, but I'm still stuck and hoping for some further clarification. Results from ...
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42 views

When should I use contrast coding?

I have a - so I guess - a simple question: I am using Stata 13 and I am running a Tobit model to understand differences in firm performance. Among others, I am controling for firm types $T_i$- i.e. ...
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1answer
26 views

Interactions between levels in lme4

We are implementing multilevel models in lme4 and have a question about how to handle cross-level predictors. This is a psychology experiment where individual participants come into the lab and ...
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1answer
68 views

Interpretation of simple slopes

This question relates to the same analysis that I posted about yesterday, but the question is different, so I have started a new entry. I have conducted a moderation analysis by entering continuous ...
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1answer
30 views

Why is multi-way ANOVA typically taught with reference to interaction terms, whereas multiple regression isn't?

For instance, reference to an interaction term will almost always be made when Two-way ANOVA is taught. However, when considering a regression with two continuous predictors and one continuous ...
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Performing Interaction Contrasts on mixed-models in R

I need to run interaction contrasts on the following data set. It is a mixed design with the dependent variable a questionnaire score measured across five test days (within-subjects variable 'Day'). ...
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98 views

Significant interaction but non-significant slopes?

I have conducted a moderation analysis as follows: x (continuous independent variable, centered) m (continuous moderator, centered) y (dependent variable) By entering x, m, and the product of x and ...
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23 views

Is it acceptable to remove a main effect in an interaction model where the variable is only populated for a treatment group?

I am trying to construct a model to predict how a treatment will affect new units in the presence of certain covariates. For purposes of explanation, let's suppose the units are bacterial colonies and ...
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1answer
62 views

Interpreting main effects in the presence of an interaction in logistic regression

I am carrying out logistic regression to determine which factors affect whether lasers are effective bird deterrent devices. In my model, a success (1) is when a bird flies away and a failure (0) is ...
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1answer
27 views

Interaction effect in a multiple regression vs split sample

Until now I thought I understand an interaction effect. I interpreted it always as the change of slope conditional on some dummy=1. Perhaps I am wrong. I have a model and add an interaction dummy D, ...
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Force specific interactions in Package 'earth' in R [migrated]

I am using the 'earth' package to construct a Multivariate Adaptive Regression Spline model. Using the earth function, is there a way to allow interactions ONLY between certain predictor variables? ...
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Determining need for interaction term from graphs

I am trying to create a regression model for mpg vs 4 variables from mtcars dataset: mpg ~ wt + disp + hp + cyl I have following 4 plots between these variables: ...
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1answer
38 views

Should I include interactions on the log-scale when I'm only interested in the probability effects?

I want to fit an unordered categorical (multinomial) regression model in which I have two categorical predictor variables. It makes sense that these two variables interact with each other. However, ...
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1answer
27 views

Interaction terms in cross-sectional regression

I have a question regarding the use of interaction terms in a cross-sectional regression model. Currently I am working on a study for which I have a sample consisting of roughly 500 observations, ...
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Regression controlling for the influence of group

My goal is to check whether reading measures are predicted by audiovisual measures, beyond some reading-related measures. So, for example, I have a reading accuracy measure and I want to see whether ...
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105 views

Mean centering - before regression or observations that enter regression?

I am using Stata 13 to estimate a simple model with interaction terms. To give the coefficients a meaningful interpretation at zero, and to avoid multicollinearity, I am mean centering variables. I ...
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How to constrain higher-order interaction terms in hierarchical bayesian regression models with multiple categorical and metric predictors

Greetings Statistics Wizards! I am building a hierarchical bayesian regression model in which the predicted (y) variable is metric (numerical, continuous) and the predictor variables are both ...
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What is a valid post-hoc analysis for a three-way repeated measures ANOVA?

I've performed a three-way repeated measures ANOVA; what post-hoc analyses are valid? This is a fully balanced design (2x2x2) with one of the factors having a within-subjects repeated measure. I'm ...