Questions tagged [main-effects]

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Why type III sum of squares is not recommended to use when there is significant interaction?

I did notice that in the following example, I obtained a insignificant main effect for treatment when including interaction, although the treatment is clearly effective. Any intuitive explanation? ...
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1answer
12 views

Factor Levels in a Two-Way ANOVA

I'm trying to figure out the explanations of the Effect Plots below. I believe I have figures out Figure 9a, but the explanation for Figures b, c, and d given in the textbook I do not comprehend. Any ...
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9 views

Given a specific model how would you find the possible effects and interactions of the factors?

I am looking for contaminations on two different beaches N and S at two different times T1 and T2. Where it is suggested that Beach N has a higher risk of contamination than beach S and the levels ...
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1answer
189 views

Main effect vs simple effect

In the following linear model: $y = \beta_0 +\beta_1 x_1 +\beta_2 x_2 + \beta_3x_1x_2 + \epsilon$ what are called $x_i$? The term $x_1x_2$ is the interaction. In ANOVA, $x_i$ are named "main ...
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15 views

Is a "deviance table" equivalent to the type 2 or type 3 ANOVA?

I was taught, that ANOVA assesses the main effects and interaction effects of a linear model. In other words, it jointly tests appropriate model (with categorical IVs) parameters, telling us, if all ...
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1answer
18 views

Using Orthogonal Main Effects Plan to select profiles for conjoint analysis

I am trying to create a code in Python to select orthogonal profiles given some attributes and levels. For eg: ...
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7 views

Prediction of a null-effect in the interaction but a main effect of condition

Let's assume I have 2 groups of subjects (A, B) and I test these groups in a task where I measure reaction time (RT) in two conditions (C1, C2), which I will analyze with an Anova. Is it legit to ...
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157 views

Three-way MANOVA Interpretation

I'm interpreting a three-way MANOVA as part of my research, and have come across an interpretation challenge, with three independent variables (Factor A, Factor B, and Factor C) and two dependent ...
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15 views

The procedure of adding interaction terms in regression models

What is the more sensible way to add interaction terms in regression models? I have a basic model which includes only the main effects. To add interactions to the basic model, do I add all of them at ...
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1answer
216 views

Why are Simple Effects only used when the interaction is significant?

I have conducted a 2-way ANOVA and obtained a significant Main Effect in IV1 and IV2, but a non-significant interaction. Following that, I have analyzed IV1 using a test for Simple Effects and ...
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1answer
58 views
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34 views

Interaction effect in logistic regression

I have applied logit model, where my dependent variable is Emp (Employment) 1 if employed otherwise 0, and used level of education and Health status as independent variables where: Education consist 6 ...
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71 views

How to handle interaction in this longitudinal model?

Let's assume we have the following result of a longitudinal experiment, which evaluates the effect of a fertilizer over time. The dependent variable is about "poor condition". The higher ...
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1answer
125 views

Interpreting growth curve analysis (GCA) main effect in light of interaction (eye tracking data)

I have fit parabolas to two groups in a growth curve analysis (GCA) of eye tracking data using orthogonal polynomials (essentially by following Dan Mirman's example for his paper with Magnuson in 2009,...