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

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3
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1answer
87 views

How to explain control variables and interaction effects

I'm a bit stuck on running a GLM between 3 continuous variables in R. I can't make them categorical as it removes the significance. I have two questions. I'm analysing data on eggs. I had read that ...
0
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0answers
11 views

How to normalize interaction terms?

I'm training a classifier for a supervised classification problem. Some of my features interact, how should I normalize these interaction terms? For example, if x1 and x2 interact, the interaction ...
0
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0answers
13 views

3x2 design - data analysis ANOVA/MANOVA? How to add interaction in the model?

Discription of experiment I am researching "The effect of review valence and brand commitment on consumer's purchase intention" for my university thesis. I conducted a 3x2(no review/positive ...
1
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1answer
30 views

Interaction in Survival analysis

I am a physician and clearly not a statistician (I try to understand why and how to perform the right analysis, but I don't understand the formulas). I am using SPSS v.19 in analyzing my data. I try ...
0
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0answers
31 views

Cannot do Tukey test in multcomp

After performing series of linear mixed models in lme4 to justify which model with which level of interaction to be used, now I would like to do the Tukey's test for multiple comparison. So first, I ...
0
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0answers
18 views

Two-way interaction: interpret output from LMM in lmer

I have asked a question in this topic relating interpreting two- and three-way interactions in this link: How to interpret 2-way and 3-way interaction in lmer? ...
1
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1answer
44 views

How does the interpretation of main effects in a Two-Way ANOVA change depending on whether the interaction effect is significant?

As far as I can tell this question has never been asked before. There are several questions that touch on related issues, but as far as I can see none of them have provided a definitive answer to this ...
0
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1answer
36 views

Interpreting a significant 2-way interaction with post-hoc tests

I'm analyzing reaction time data from a repeated measures ANOVA with the following design: Factor 1 (between-group): GROUP (controls, clinical) Factor 2 ...
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0answers
19 views

post-hoc test on mixed-effects model

I have an experiment with bacteria for which I measured growth curves of several bacterial clones in two different types of media (treat). I then extracted several growth parameters from the curves ...
0
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0answers
3 views

How to create three-way interaction graph in R (I have example of graph)? [migrated]

I would like to create this kind of graph for my data (categorical IVs and continuous DV). How can I find the formula that helps me to run this?
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0answers
10 views

Including non-hypothesized interaction terms in moderation analysis

I am running a moderation analysis using hierarchical linear regression. I have two predictor variables and two moderating variables and I am interested in their interactions to predict an outcome. My ...
3
votes
1answer
57 views

Understanding coefficients in summary output of logistic regression in R

This question is about understanding the logistic regression output using R. Here is my sample data frame: ...
0
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1answer
26 views

Interaction: ignore two-level if three-level is significant in every case?

I am using lmer in R to run LMM. My DV is continuous and my IVs are categorical. Many statistician said if the three-level parameter is significant, I cannot interpret the two-level parameter. Does it ...
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0answers
36 views

Setting up a naiv tensor product B-spline example

I've simulated data according to $y = \text{sin}(2\cdot(4x-2))+2\cdot\text{exp}(-(16^2)(x-0.5)^2)+\epsilon$ where $\epsilon \sim \mathbb{N}(0,0.3^2)$ By evaluating the ith B-Spline of degree $k$, ...
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0answers
16 views

Interpretation of three-way interaction in an output of lmer

I am using lme4 to run a three-way interaction model. I have three independent variables: animal (rat, lion, dog), color (red, green, blue) and sex (male, female). The baselines are as follows: ...
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0answers
12 views

Moderation using ANCOVA

I am performing a repeated measures ANCOVA with Mood Scores as the dependent variable, Image Condition as the independent ...
3
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0answers
24 views

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 ...
2
votes
2answers
69 views

A good source to understand interaction in LMM?

I would like to know more about interaction in LMM using lmer. Can you recommend me any books, articles, websites?
1
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1answer
62 views

What is the meaning of the beta-coefficient for an interaction term in a crossover study?

I have asked a similar question here: stackoverflow I am puzzled by the interpretation for an interaction term. In my data my Y is an interval variable with the health outcome of an experiment. I have ...
2
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0answers
29 views

Interaction term is insignificant but the interaction plot shows signs of signficance

So, I ran an ANOVA on a dataset which contains over 4500 data points. Without getting into too much detail, I was wondering if there is a simple explanation to this: The p-value for my interaction ...
2
votes
1answer
67 views

Interaction term in a linear log model

I am using a linear-log model to test whether overseas development assistance and remittances positively affect FDI in cases of good governance and financial market development. Let's say I want to ...
3
votes
1answer
51 views

Finding interactions using randomForest

I am trying to use randomForest in R to find interaction terms to add to a model. My plan was to fit trees with maxnodes=4 (two ...
3
votes
1answer
59 views

Interaction effects in non-linear models

I have a general question about interpreting interaction effects in a non-linear model. I understand the reasons Ai and Norton (2004) suggest using the stata inteff command to help interpret ...
4
votes
1answer
79 views

R gls() vs. SAS proc mixed with interaction: Why does R complain about a singular matrix when SAS does not?

I like to keep analyses all in SAS or all in R when I can help it and lately have been using R more and more, but there's one analysis that I do somewhat routinely that has given me trouble in R. I ...
0
votes
1answer
19 views

Interpretation of interaction term in R lm(): .L .Q [duplicate]

I ran a regression in which I have an interaction term of two factor variables. The one of the variables has 2 levels: Condition_A & Condition_B (therefore the first one is the reference ...
2
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1answer
148 views

The main effect will be non-significant if the interaction is significant? [duplicate]

I am using linear mixed models to identify important factors, and it turns out that: A: significant B: not significant ...
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0answers
20 views

how to test interaction with anova?

In a two-ways anova we can decompose the total sum of square in its components. SST=SSE+SSA+SSB+SSAB It is a common notation in the field so it should be clear ...
2
votes
1answer
76 views

Help interpreting logistic regression

I'm new to R and logistic regression and have to admit that I don't really know how to interpret the result. I'm trying to compute a pretty simple model with 2 predictors (A and B). When I first try ...
2
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0answers
18 views

plotting a main effect in the context of a significant interaction

I have a model that has two significant main effects and where the interaction between the two variables (age and %gray) is also significant in a multiple regression. When the interaction (age * ...
0
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1answer
23 views

How to calculate and evaluate estimators in decomposing interaction models to subgroup models?

Suppose we have a simple interaction model (ignoring error terms for simplicity) Y = b0 + b1X + b2Z + b3X*Z in which Z is the dummy variable. The model gives values and s.e. of these coefficients. ...
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votes
3answers
186 views

ANOVA shows no significant interaction effect, but Tukey's Test shows significant differences between groups?

I am a PhD student but I am having a hard time understanding certain aspects of statistics. I just ran an ANOVA and I got no significant interaction effect between Density (0 and 20) and Species ...
0
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1answer
49 views

What does it mean to have two intercepts? [closed]

Suppose I am modeling the sales for multiple products for multiple stores. What is the difference between: \begin{align} \text{Sales} &= \beta_{0}(\text{Intercept × Store}) ...
2
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0answers
29 views

How to create a covariate × time interaction term in Cox regression?

In Cox regression, it is sometimes inevitable that the strength of a predictor will vary across time (Singer & Willett). This violates the proportionality assumption, but can be incorporated in ...
0
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0answers
49 views

Response Surface Data Mining methodology

Recently, I used the methodology of response surface data mining proposed by Lee and Shin (2010) for job stress evaluation. in their study they considered about 80 factors affecting job stress and ...
1
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0answers
30 views

How to find the most important factors or combination of levels in a finite data set

I’d like to discover which “calendar factors” (e.g. day of the week, month) have the strongest relationship with whether or not a particular product is sold at least once. For days when the product ...
2
votes
2answers
97 views

Comparing interaction effects using different variables. Possible?

I want to compare which are the "most important" interaction effects (in a data driven way, I realize that it is has downsides). I realize that for substantial researchers this does not make sense, ...
0
votes
1answer
21 views

Cross-Level-Interaction without varying slope in Multilevel

Is it useful to include cross-level-interaction in multilevel (hierarchical) models without varying slopes (only varying intercept)? A short example in R: ...
1
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2answers
145 views

Marginal effect of squared variable in Probit Model

I want to estimate the following probit model $employed_t=\beta_1 age + \beta_2 age^2$ and I use the Stata code probit employed c.age##c.age Using the command ...
0
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1answer
57 views

How to interpret regression estimates

I am studying the effect a certain chemical and age on an outcome. As variables, age is a factor of with levels 1, 2, and 3 and ...
1
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1answer
28 views

Coefficient marginal to interactions in linear regression

Consider this model: $$y = \beta_0 +\beta_1x_1 + \beta_2x_2 + \beta_3x_1x_2 + \varepsilon$$ Somebody told me today that the coefficient for the main effect of $x_1$ (i.e., $\beta_1$) will be ...
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0answers
12 views

Anova: 'Base case' for interactions when regressing upon dummies

Say I want to perform a two-way ANOVA, and I want to use the sources A, B . For A I test at levels A1 and A2, for B at B1,B2 and B3. So when I do the analysis I regress on the dummies with, for ...
3
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0answers
37 views

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 ...
0
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0answers
21 views

Cox regression with interaction giving NA values, how to interpret? + Choosing covariates based on p-values

I am working with a dataset with 12 covariates(categorical). The covariates have different Levels, some are from 0-5, and one has as much as 0-11 categories. I started with a univariate analysis to ...
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0answers
30 views

How to visualize an interaction from a GLMM: use whole model to obtain predicted values or just factors in the interaction?

I need to plot an interaction between two continuous factors for interpretation. I am using the wireframe function in the lattice package and plotting the predicted values from the model with the best ...
2
votes
1answer
27 views

Is including the main effect of the covariate enough?

Is simply including a covariate in a model (ANCOVA) enough for variance in the DV due to it to be factored away? Or do the higher order interactions of the covariate with the other factors of the ...
3
votes
3answers
135 views

Interaction term in linear regression

I have two variables, and the relationship between them looks like that in this plot: ggplot(mtcars, aes(wt, mpg)) + geom_point() The relationship between ...
0
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0answers
25 views

Mediated, moderated mediation?

I have a significant effect of interaction $AB$ in $Y = A + B + AB + covariate$ Is it possible to do a mediation analysis to see if $AB\rightarrow Y$ is mediated by $A\cdot covariate$? Is it valid ...
0
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0answers
29 views

How to calculate required sample size to detect a significant interaction between two continuous variables

I am planning to do a statistical power analysis, and I would like to know how to calculate the required sample size to detect an interaction between two continuous predictors in the presence of other ...
1
vote
1answer
38 views

How to measure the influence of an index on the correlation between 2 other indices

I have 3 raster datasets. All 3 are values of continuous indices varying between 1 and -1. These are satellite measurements of the same area, divided in a raster. Each cell has a value for every ...