# Tagged Questions

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### Which one to use Splines / Interaction or both?

I am modeling a binary event of whether a sale will happen or not for an online retailer. I have millions of clicks to refer to. Needless to say the rate of sales happening is very very low (<1%). ...
62 views

### How interactions between explanatory variables can be found using binary recursive partitioning?

I would like to investigate interactions between my explanatory variables prior to building a statsitical model. Apparently it is possible to do it in R using a regression tree (library: tree). This ...
63 views

### How to address and acknowledge a significant interaction that has little practical meaning

I am building a model with a highly significant interaction. This interaction was one of our main hypotheses. It is clear, however, that the form that the interaction takes does not represent a ...
81 views

### Fitting lower-order interactions with higher order main effects

We have 2 continuous predictors in a regression model, and both have significant quadratic terms. Our main hypothesis we'd like to test is (generally) whether there is an interaction between these ...
46 views

### Interpreting logit regression with both continuous and categorical variables

I have a logistic regression like this: ...
53 views

### Interaction of variables in regression

I have two variables that predict fraud behavior (dependent variable). The independent variables are perception of fraud being wrong (1-5) and probability of being caught (1-5). The dependent variable ...
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### Linear regression with independent variables with varying proportions

I am looking to do a linear regression on two independent variables that will be present in varying proportions. For example trying to do a linear regression on $Y$ which is payment behavior (payback ...
61 views

### Marginal effect in model with interactions

I am running cross-sectional regressions of the type $$Y_c = \alpha + \beta X_1 + \gamma X_2 + \delta_1 X_3 + \delta_2 X_1 X_3 + \delta_3 X_2 X_3 + e_c.$$ My theoretical model implies that ...
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### Interaction wipes out my direct effects in regression (non zero variable)

I have the following regression $children = \beta_0 + \beta_1 \log(earnings) + \beta_2 grandparents + \epsilon$ and $\beta_1>0$ with $p$=0.01 and $\beta_2>0$ with $p$=0.01, and N is large ...
76 views

### A summary of different cases of interaction effects, how do you interpret?

I know there are lots of questions/answers about dealing with interaction effects in regressions on this site, but I think there is a need to summarize a bit. I don't know if there is a standard way ...
127 views

### Use lag operators with interaction term, is it correct?

I'm sorry I make reference to Stata here, but it's just to illustrate the point, the question is about whether it is correct or not using lagged variables in interaction terms. I have a linear model ...
144 views

### How to test whether linear models fit separately to two groups are better than a single model applied to both groups?

My question is how to tell if two regressions explain the data better than one. Let me be more concrete with an example (which I'm making up as I go, it's not meant to be plausible). Say I'm ...
116 views

### Compare 2 regression lines in R

I have the following data frame ...
439 views

### Why could centering independent variables change the main effects with moderation?

I have a question related to multiple regression and interaction, inspired by this CV thread: Interaction term using centered variables hierarchical regression analysis? What variables should we ...
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### How to interpret interaction between 2 independent variables with ANCOVA?

I'm measuring the influence of the use of male gaze and nudity in magazines to see if girls self-objectify or not. Now, I want to determine the influence of age. ...
156 views

### Should I re-center variables when looking at moderator effect in men and women separately?

I want to see if an interaction variable in a multiple regression is significant for the whole sample, and then just for men and just for women. When I created the interaction variable for the whole ...
183 views

### ANOVA and Regression give opposite results in R

I conducted an experiment in a factorial design: I measured light (PAR) in three herbivore treatments as well as six nutrient treatments. The experiment was blocked. I've run the linear model as ...
27 views

### Spatial interaction model calibration question

I am attempting to calibrate (i.e., estimate the parameters of) a spatial interaction model where one of my interaction terms is a composite of other terms. An example might be $I_{ij}$ = ...
138 views

### How to interpret the significant interaction of two non-significant main predictors?

I have two non-significant main binary variables in my binary logistic regression model, but their interaction is significant. The variables are centered and no multicollinearity is the case (all VIFs ...
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### Fractional Polynomial interpreting interaction terms

Background: I have developed a logistic regression model where I am trying to analyze the effect of socio-economic data of a family on their probability of receiving a home loan. I have used ...
339 views

### Interpretation of interaction effect in negative binomial regression

I am trying to interpret my interaction effects, which are all negative. One example: Experience (variable A) x absolute size of the acquired knowledge base (variable B): B= -0.002, exp(B)= 0.998. ...
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### Nonsignificant interaction still causes main effect to flip?

This is my first post so forgive me if this is question has already been asked. I searched around the forum but didn't find anything specific to what I'm looking at currently. I'll keep things as ...
79 views

### Regression interaction w/ dichotomous predictors: Two levels, two coefficients?

this question is about a way of presenting the results of an interaction I thought of, and I'm looking to see if it makes sense. If there is a better way to do what I'm trying to do (or if what I'm ...
177 views

### Visualizing an interaction effect of a Logistic Regression Analysis (in SPSS)

What would be the best way to go about visualizing an interaction effect of a Logistic Regression Analysis (preferably using SPSS)? There is a significant interaction between one interval (HDI) and ...
50 views

### R module for creating plots of prototypical individuals from fitted models?

In order to help interpret fitted models â€” especially those with interaction terms and non-linear components â€” I've found it useful to plot predicted values of a dependent variables for what we might ...
79 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 ...
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### 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. ...
86 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
984 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: ...
47 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 ...
215 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 ...
148 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 ...
355 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 ...
439 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 ...
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### 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 ...
131 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 ...
171 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 ...
198 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. ...
180 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) ...
421 views

### Regression with multiple endogenous regressors instrumental variables and interaction terms

I am running an two regressions one with a binary dependent variable (y) and one categorical. My data is cross sectional so to deal with issues around causality, endogeneity (reverse causality) and ...
73 views

### Constructing a measure versus using an interaction

My dataset is sports data and the outcome variable is wins in a season and I am trying to see the affect of the characteristics of the players on the team on this outcome. My question is, is it easier ...
118 views

### What to do when the predictors do not accord with common sense/literature, but the model is fine/best according to log likelihood and LRT?

I would try to clarify the problem and then ask the questions. The problem (variable names are masked due to confidentiality): I ran a binary logistic regression, in which there were 5 ...
199 views

### Should I include an interaction term for a covariate if I expect it to be correlated with one or more of the variables?

I'm fitting a linear model where the response variable is a measure of physical performance-- running speed for example-- and the predictor variables are sex and drug treatment, with an interaction ...
My interest lies in finding the "right" correlation between a continuous IV ($x$) and a continuous DV ($y$). At first I ran a simple linear regression: $$y=a+b_1 x$$ However, lots of other factors ...