A situation where the effect of an explanatory variable may depend on the value of another explanatory variable.
1
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0answers
25 views
R module for creating plots of prototypical individuals from fitted models?
In order to help interpret fitted models — especially those with interaction terms and non-linear components — I've found it useful to plot predicted values of a dependent variables for what we might ...
0
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0answers
43 views
Interpretation of the OLS regression coefficient of a proportion dependent and interaction independent variable with dummy
I have two regression models; I am not sure how to interpret the coefficients. In the first one the dependent variable is earnings management proxied by (abnormal accruals scaled by total assets), the ...
1
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0answers
54 views
Is it a true main effect if it is significant only when interaction is included?
There is a question What if interaction wipes out my direct effects in regression?. An answer was given that the true main effects are in the model without the interaction.
I have the opposite ...
2
votes
0answers
33 views
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 ...
0
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0answers
22 views
Interpreting interactions in multilevel model
I'm running a rather simple multilevel model in which I have two variables interacting at level 1. The interaction term is significant, but I'm not sure how to interpret it properly. I am familiar ...
1
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0answers
46 views
Two-way anova with interaction term: what is the point of a post-hoc test?
I have a statistics interpretation question. I've recently performed a two-way anova to identify an interaction term between my categorical independent variables (genotype + temperature) that ...
0
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1answer
22 views
How do I derive slope and intercept for each group in regression model with a categorical and 2 continuous predictor variables?
$IQ = b_0 + b_1Group + b_2Age + b_3Income + b4\times Group\times Age$
Group is dummy coded ($0,1$)
I assume that the interaction of Group x Age tests the group difference in the slope of the IQ vs. ...
2
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1answer
43 views
interaction terms in separate models?
I'm doing a multilevel mixed model with three cross-level interactions in LMER. Do all three interactions necessarily need to be included in the same model or can I evaluate them in three separate ...
1
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0answers
23 views
How to Partition An Interaction SS in ANOVA
I'm a new user of R and I'm trying to replicate Table 6.18 on page 262 in Statistical Procedures in Agricultural Research, By K. A. Gomez and A. A. Gomez. New York, Chichester, etc.: Wiley (1984). ...
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0answers
26 views
Calculating HPD for marginal effects of interactions of lmer models
I am fitting a model with lmer, using the following code:
...
2
votes
0answers
33 views
Few main variables in the best model still show multicollineairty. Should I remove them despite their importance?
I have a binary logistic regression with 5 IVs and all of their 2-way interactions. I have reduced/removed multicollinearity between main variables and their interactions by centering the main ...
0
votes
0answers
14 views
(Conceptual framework) Should confounding factors be placed in the framework?
Suppose we study the effect of a factor X on an outcome Y. We hypothesize that there may be a potential confounder Z, which may or may not be observable or present in the data. Controlling for Z is ...
0
votes
1answer
42 views
2 x 2 between-subjects design ANCOVA with non-sig. interaction effect; but profile plot shows curves crossing
I'm running a 2X2 between-subjects design ANCOVA and wonder about one peculiar thing: The ANCOVA output table reveals no significant interaction effect, albeit the profile plot shows two lines that ...
1
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1answer
61 views
2x3 ANOVA interaction no longer significant after including a covariate?
My experiment had a 2x3 design with one covariate. If I analyse the results using an ANOVA, I get a strongly significant interaction between the two main factors (p<.001). If I add the covariate ...
1
vote
1answer
38 views
After centering, interactions' effects got reversed. It was not fixed by reversing the dependent variable. What should I do?
In a binary logistic regression, I centered all the independent variables (binaries, continuous, dependent, independent, all [I have 5 IVs: three binary and two ordinal]). Multicollineariy was ...
1
vote
1answer
44 views
How to choose interactions to test when there are many predictors?
If I have many covariates $X_1, X_2, ... ,X_{15}$ in a linear regression model, how do I determine which two-way interactions to include? Obviously there would be too many potential models to do a ...
-1
votes
0answers
26 views
Why is an ANOVA interaction no longer significant after including a covariate? [duplicate]
I have initially run a 2x2x2 Anova and found some significant interaction between the independent variables. I then ran an ANCOVA where I added a covariant. I am confused with how to interpret the ...
0
votes
0answers
103 views
marginal effects (and confidence interval) for interaction variables (STATA)
I'm trying to marginal effects (and their confidence intervals) for an interaction variable.
I'm using Stata and it's panel data (pooled cross-sectional time ...
1
vote
1answer
90 views
How do I report a 4x4 ANOVA interaction
How do I report this 4x4 interaction (this is part of a 4x4x2 ANOVA)? This is an interaction between the factors grouping (Gestalt heuristics for visual grouping of compound figures) and set size ...
1
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0answers
25 views
Interpretation of main effect when interaction term being significant (ex. lme)
As an example I use "Pinheiro, J. C. & Bates, D. M. 2000. Mixed-effects models in S and S-PLUS. Springer, New York." page 225, where rats are fed by 3 different diets over time, which body mass ...
0
votes
2answers
127 views
Is there a simple rule for interpretation of Interactions (and their directions) in binary logistic regression? [duplicate]
I have a binary logistic regression with Y (a disease) and 5 independent variables (and some of their 2-sided interactions which did not cause multicollinearity). All of my single IVs significantly ...
0
votes
1answer
52 views
When is it valid to include interaction terms in a regression model? [duplicate]
I am using logistic regression to analyze some categorical data (binary response variable and categorical -- mostly binary -- predictor variables). For my model, I have something like ...
3
votes
1answer
163 views
Interpreting interaction terms in logit regression with categorical variables
I have data from a survey experiment in which respondents were randomly assigned to one of four groups:
...
0
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0answers
39 views
How to control intercept of only one IV-DV relationship in multiple linear regression
If I have a relationship between three variables (survivorship (outcome), time and dose (continuous) with interaction) how can I control the intercept for time but not dose in MLR? The reasoning for ...
0
votes
0answers
26 views
Interpreting Outputs From a Generalised Linear Mixed Model
So I am running an experiment on transmission fidelity in humans depending on information type. This works by having chains of 5 people playing a Chinese whispers type game with 4 passages of ...
0
votes
0answers
66 views
Interpretation of interaction effects for ANCOVA in SPSS
I am now evaluating the results of my experiment on what influences the likelihood of installing a specific application (continuous variable). I manipulated 2 factors: reputation of a provider of the ...
1
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0answers
27 views
Quantify mediation effect of one variable on interaction of 3 others
I would like some quantitative measure of the degree to which an observed categorical variable predicts mediates the effect of an experimentally controlled factor on a continuous DV. The situation is ...
0
votes
0answers
38 views
Do Cross-level interactions must include the constitutive terms in the 1st level?
I have an equation like the following in the first level:
$$Y = b_0 + b_1X_1$$
And in the second level, I have a variable $X_2$ which effect only makes sense on $b_1$, not directly on the mean of ...
0
votes
2answers
21 views
Selecting out main effects when locational-scale-invariance isn't an issue(?)
I'm starting a new thread to ask a specific question that I'm left with after reading this old, good thread:
Do all interactions terms need their individual terms in regression model?
The gist of ...
2
votes
1answer
162 views
Moderation in repeated-measures design?
Context: Both dependent $(Y_1,~Y_2,~Y_3)$ and independent $(X_1,~X_2,~X_3)$ variables were measured repeatedly at three time points, $\text{Time}_1$, $\text{Time}_2$, and $\text{Time}_3$. Moderator ...
1
vote
1answer
82 views
How to calculate the standard error of the marginal effects in interactions (robust regression)?
what I am interested in learning is how to calculate the std error of the marginal effects of a X variable when it is part of an interaction, especially in robust regression.
There are tipically two ...
0
votes
0answers
27 views
Incoherent ANCOVA?
I am doing an ANCOVA model in order to explain the gap in a given distance. So I have a control group, and I have several quantitative variables, right now I am trying to evaluate the impact of the ...
2
votes
1answer
79 views
Interaction terms in poisson regression
I'm confused about the interpretation of interaction terms in poisson regressions. Here's a hypothetical dataset
...
0
votes
1answer
53 views
0
votes
2answers
85 views
Should I keep the interaction term?
I am doing research on mortality. I am running cox regression and I am adjusting for 40 variables which are proven in the literature to be related with mortality. My main exposure is X. In my final ...
5
votes
1answer
143 views
Does every log-linear model have a perfectly equivalent logistic regression?
I am trying to fit a log-linear model to a large number of variables from survey data. There are some reasons that it might be preferable to fit logistic regressions to that data instead. Several ...
2
votes
1answer
147 views
Test whether simple slopes are different from zero in 3-way interaction in multiple regression
I'm trying to test whether 4 different slopes from a 3-way interaction in multiple regression are significantly different from zero. The four lines are plotted at 2 levels of each of the 2 moderators ...
2
votes
2answers
143 views
In my logistic regression model one of the independent variables is redundant with the interaction term. How should I deal with it?
In my logistic regression is the dependent variable a dummy variable and I also have two independent variables. One of those is a dummy variable and the other is a metric variable. I also suppose an ...
0
votes
0answers
19 views
Change in S.E of one variable when interaction term added to Binary Logistic Regression [duplicate]
I have 6 predictor variables and have carried out a binary logistical regression. I found that most variables significantly predicted the DV. However, I then wanted to find out if there was a ...
1
vote
2answers
94 views
Inconsistent beta values in regression analysis due to change in categorical coding
I have three terms in my regression models:
gender (categorical data),
centeredmeanB (quantitative data)
and the interaction term gender * centeredmeanB.
I noticed than the way I coded gender ...
2
votes
0answers
59 views
Swapping X and Y in a regression that contains a grouping predictor?
Suppose I'm doing a linear regression and I want to investigate how the association between a predictor X and a response Y changes according to levels of a 2-level factor G. The model would look like ...
2
votes
3answers
288 views
Reporting interaction effect for a 2x3 ANOVA
I have used a 2x3 mixed between-within subjects ANOVA to assess the impact of three feedback conditions (Grade, Comment and No Feedback) on participants’ scores on the Specific-Self Efficacy Scale on ...
1
vote
1answer
177 views
Interpreting this regression coefficient
Quick background:
I am working on a political science project that involves analyzing the impact of different variables on the extent to which a candidate mentions other users when he or she tweets.
...
1
vote
1answer
52 views
quantifying interaction between variables in an equation
What do I need to measure interaction between variables in a particular equation?
For e.g.
Me just taking 50 grams of protein everyday will help me health wise.
Me just doing exercise for 1 hour ...
1
vote
1answer
79 views
Issues when using interaction term with a lagged variable in R
Today I tried to estimate models using both plm and pgmm functions in the plm R package, with an interaction between ...
1
vote
0answers
53 views
Test for whether a change is different in direction for subgroups?
I have a (large) population on which I randomly split into groups, and subjected one group to an experimental condition (call it change A) which demonstrated a significant improvement in a target ...
0
votes
1answer
117 views
Two-way ANOVA repeated measures
I would like to know, if you got a significant interaction in a two-way repeated measures ANOVA in SPSS, how can you visualize the interaction (especially using syntax)?
2
votes
1answer
176 views
How to interpret overlapping interaction plots?
I have an interaction plot that seems to be overlapping on top of one another, what does this signify?
4
votes
3answers
170 views
Two significant covariates in coxph analysis: exploring whether the two covariates interact significantly
I am using R 2.15.2 GUI1.53 64-bit on MacOSX 10.5.8 to perform these analyses. I am a molecular biologist by training, not a statistician, so all this analysis represents my own bootstrapped learning ...
0
votes
1answer
103 views
Problem with interaction variable for logit regression
I have a short question regarding interaction variables:
In a logit regression with 2 independent dichotomous variables (A and B), both variables are significant. By including the interaction (AxB) ...
