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

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Using interaction terms in an MCMCglmm

I am using MCMCglmm models in R, with hierarchically nested data. The basic structure of the data is as follows - each dyad is a unique combination of focal/other: ...
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1answer
14 views

Explaining Non-Significant Moderations

Schools often teach us how to conduct and interpret Moderations. What they don't teach us is how to explain why a moderation didn't work out for statistical/methodological reasons. Assuming that the ...
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14 views

Sample size for a moderated hierarchical multiple regression analysis?

I am having a challenging time finding out the necessary sample size for a moderated hierarchical multiple regression analysis. The first five steps of the regression will include the 17 variables ...
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27 views

How to interpret 3 main effects when an interaction exists for only two of the variables?

I've been searching for interpretation guidance regarding the below problem, but all the resources I've seen have been fully crossed (i.e., all variables included in the interaction term). Below is a ...
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1answer
16 views

Metafor package: RMA and testing for interaction in two studies (Altman & Bland 2003)

I have traditionally used this simple test of interaction (http://www.bmj.com/content/326/7382/219) for comparing effect sizes between studies, and I would like to start performing it in R. Although I ...
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9 views

in a partial mediation relationship, can the independent variable and the mediator moderate each other?

Let's say age predicts experience, and experience predicts perceived reputation of doctor. Age also predicts perceived reputation directly, and moderates negatively the relationship between experience ...
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7 views

Is this a confounding interaction: using demographic data in a fractional factorial design?

I've created and run a choice experiment (conjoint analysis) using a fractional factorial design 3 x 3 x 3 x 3 (four factors with three levels each). I also collected some demographic data (age, ...
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40 views

Interaction terms and effect sizes in multiple regression

I know there are similar questions on here, but I can't quite find an answer that covers all of what I need. I am running multiple regression in r with two predictor variables and sometimes an ...
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16 views

how to interpret Interaction term in generalized linear model [duplicate]

I have an experimental condition (dummy-coded) as an categorical predictor, and one continuous predictor variable (treatment frequency). The dependent variable (Y) is consumer satisfaction This is ...
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20 views

Interactions between Dummy codded categorical variables in R

I have estimated a mixed-logit model in R.Here are my Results ...
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1answer
38 views

How should I interpret a factor that is significant both (1) in linear form in interaction with another factor and (2) in its quadratic form?

Our study aims to identify and understand how several ecological factors relate to parasite abundance in a colonial animal. However, we are uncertain on how to interpret a factor (density) that is ...
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1answer
56 views

Design of Experiments

Suppose a dermatologist wants to study the effectiveness of two different preparations of a skin lotion using two different forms of application, such as one versus two applications per day. She has ...
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2answers
64 views

Graph with 2 interacted continuous predictor vatiable

When using glm(link=logit), I detected a significant interaction between two continuous predictor variables. How can I present the results visually using R?
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2answers
84 views

Interpretation of multiple logistic regression with interactions in R

I am trying to look at whether 2 variables (one dichotomous categorical and one continuous) predict the occurrence of a dichotomous categorical dependent variable. ...
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3answers
36 views

Results with and without interaction

I'm working on an analysis with another person. First we did a logistic regression with study group and variable X. They were both significant. Then we added the interaction between study group and X ...
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1answer
30 views

Fractional Factorial Design

In a $2^5$ design, it is believed that only the main effects $(A,B,C,D, E)$ and $AB,AC$ interaction effects are non-zero. I need to construct a fractional factorial with minimum number of runs which ...
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1answer
26 views

$2^{5-2}$ Design : Alias Structure

$2^{5-2}$ Design Design Generators: $D=AB\quad E=AC$ Defining Relation: $I=ABD=ACE=BCDE$ $$\text{Aliases}$$ $$A=BD=CE=ABDE$$ $$B=AD=ABCE=CDE$$ $$C=ABCD=AE=BDE$$ $$D=AB=ACDE=BCE$$ ...
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0answers
33 views

Interactions in multiple regression

I would like to predict BMR or Basal Metabolic Rate (energy expended by the body while awake) using the predictors age, weight, height and gender. Please suggest the interactions that I should be ...
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1answer
114 views

How to interpret non-significant interaction term in linear regression?

I have difficulties interpreting an interaction term in a linear regression with regards to my hypothesis. Consider this basic example: H0: Better school grades lead to higher income and this ...
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0answers
27 views

The a priori power of test for a simple effect within a 2x2 ANOVA

I need to know about the power of a simple effect that follows from a 2x2 ANOVA interaction. Let's call the factors in this design GROUP(Patient, Control) and MANIPULATION(Expectation, Random), ...
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21 views

Significance of linear combination of two insignificant regression parameters

I'm running a model with an interaction term, of the general form: $Y=b_1X_1+b_2X_2+b_3X_1X_2$, whereby $X_2$ is a dummy variable and $X_1$ is continuous. Neither $X_1$ nor $X_2$ turn out as ...
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26 views

Not normally distributed dependent variable in moderator analysis

I have been running a multiple moderator analysis in a pretty simple model. X are Google search queries normalized to 0-100. Y are the new registrations of cars in one country and one moderator. ...
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9 views

Measured moderator, which is influenced by an independent variable

I have a measured variable, which is found to be influenced by an independent variable (i.e., experimental conditions). I will report this in the first part of the result section. Also, as an ...
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25 views

Interaction in regression [duplicate]

In my regression model of BMR on age (yrs) , gender (1=male, 0=female), height and weight. The regression equation obtained is: BMR = 1232.059+13.281 weight+3.954 age+192.214 male-3.471 age:gender. ...
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1answer
32 views

AICc and K for categorical factors and interactions

I am new to multimodel inference. I am trying to create a model that has multiple categorical factors and possible interactions. For example say that my model is... Y ~ X1 + factor(X2) + ...
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1answer
43 views

what is the difference between collinearity and interaction?

I cannot differentiate clearly between "interaction" and "collinearity" in multiple linear regression. For me these terms are related but not the same. I have searched the forum but could not find ...
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1answer
44 views

Omitting a moderator

I'm wondering what the effect is if I don't include moderators in my model? Is this the same or different from an omitted variable bias? I am having a hard time grasping this conceptually. More ...
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1answer
30 views

Is it acceptable to not include high-order interactions (3-way and above) in the model when they are not by themselves of interest?

Is it acceptable to not include high-order interactions (3-way and above) in the model when they are not of interest and not part of the hypothesis that is being tested? NB. I am not talking about ...
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3answers
52 views

Covariate no longer significant after inclusion of interaction term

I'm trying to interpret some results here, and just want to make sure that my logic is sound. I'm predicting a binary outcome with a categorical predictor (gene level coded as 0, 1, or 2 dependant on ...
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3answers
94 views

I do not have hypotheses for my research and I have got only categorical data. what kind of data analysis can i conduct? also

I do not have hypotheses for my research and I have got only categorical data. what kind of data analysis can i conduct for correlation between variables? also is chi-square used only for hypotheses ...
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1answer
33 views

Find the amount of variation due to another covariate

I'm trying to explain a binary outcome (cardiovascular disease) with a categorical predictor (gene level, coded as 0, 1, or 2 depending on the number of risk alleles present). I'm trying to determine ...
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12 views

Should I run Hierarchical regression to test moderation? Why?

I am an undergraduate student who currently preparing for my thesis paper. In my design, there is total 4 variable (1 predictor, 1 moderator and 1 outcome variable, all of them is in continuous ...
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42 views

Statistical Analysis help for thesis - Correlation, Probit, Tobit and Moderation

Hello CrossValidated users! I am writing here cause I need some guidance on my statistical analysis which has turned out far too complex for my basically begineer stats skills and my self research. ...
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25 views

Interpreting results from a mixed model with interactions

I need your help interpreting my model's results. To make story short, I have a continuous dependent variable $Y$, and two factors $A$ and $B$, each with $2$ levels $(A_1, A_2, B_1, B_2)$. My main ...
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3answers
59 views

Ratio of explanatory variables in multiple regression

I wonder if anyone has any links or advice on specifying a ratio of two explanatory variables in a linear regression? That is, specifying the two independent variables plus their ratio. We have data ...
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0answers
19 views

Factorial design for interactions with ordinal DV

I want to make a 4 question, multiple choice survey in which each question asks about an analogous range of actions for slightly different scenarios. Each participant would only be administered the ...
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0answers
26 views

main effect and interaction effect

I faced difficulty with my data analysis output. I had two factors with split plot design. Separately, the main effect of the two factors on soil pH was significant. But their interaction effect was ...
2
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1answer
37 views

Metafor package: Interpreting rma model with two (or more) moderators.

New user of both stackexchange and R here. My questions are about mainly about interpretation, and my dataset is quite large, so I have not included my dataframe. I have two queries (in bold). Using ...
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1answer
45 views

How to run main effects and interactions in a stepwise regression?

I am using multiple regression with the backward elimination method. I have one control variable (social desirable responding) and four predictor variables (gender and three self-esteem constructs). ...
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2answers
22 views

Interaction between variables

I would like to regress basal metabolic rate (BMR) on height, weight, age and gender. How do I do this taking into consideration the interaction between the variable? Wouldn't I have to consider ...
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1answer
48 views

Can I compare two regression coefficients

I am comparing treatment outcome to two therapeutic treatments. Specifically, I am looking at how attachment moderates the relationship between therapeutic alliance and outcome. I hypothesize that the ...
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0answers
12 views

Interaction between percentage and population size in a regression

Assume I have a regression type model. Are their any statistical and/or substantial reasons NOT to include a two-way interaction which consist of a percentage and the corresponding population size. ...
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53 views

Interpreting / understanding intercept and slope values for an interaction using summary output in R

In R, using lme4, I am using a mixed model to test how a response (mode; continuous and normally distributed) is affected by a covariate (species richness (sr); continuous and normally distributed) ...
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1answer
62 views

Mixed model interaction (covariate+factor): How to interpret posthoc table output in R package phia?

In R, using package lme4, I have used the following 2 mixed models to determine I have a signifacnt interaction between a covariate (continous, normally distributed) and a factor (three levels: ...
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11 views

hierarchical logistic regression Block non-significant, interaction significant

I'm using hierarchical logistic regression and having some difficulty. Im trying to predict self-harm vs none based on IVs age, gender, alcohol, educational attainment. They are all yes/no except ...
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8 views

Correction for interaction model as it is significant in MR

I have used 1 DV and 5 IVs. I performed MR to test a model, entered age and gender in first block, IVs in second block, and interaction terms in third block. All the models are coming significant. How ...
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1answer
41 views

How to confirm a two-way interaction in a three-way ANOVA model using SPSS

I have two groups of subjects, both undergoing two experimental conditions, and data are collected at two time points: pre- and post- condition. I run a 3-way ANOVA, with one between subject factor ...
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22 views

assess the interaction of two independent variables, on the dependent one

I have a set of laws/policies that overlap with each other through time (for example one started in 1990 and finished in 2001, and the other started in 1995 and finished in 1999). I want to examine ...
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1answer
33 views

Interaction model significant in multiple linear regression

This question is not about interaction effect, but about interaction model in Hierarchical Linear Regression. I have 1 DV and 5 IVs. I want to see which of the IVs is significant predictor of DV. ...
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15 views

Does it make sense to only drop a specific level of a categorical variable? [duplicate]

I don't have SAS and the dataset with me, so I made up this table (from my memory). Basically this is what I got: After deciding to leave the variable $age$ and $risk$ in my model, I created this ...