## When is it necessary to compare treatment means in a two-way ANOVA model

This study is about how different treatments affect the quantity of some protein in the blood. The explanatory variables are categorical (3 different treatments, T01, T02, T03; trtgrp); the dependent variables are the protein level (continuous, logvncsf). 30 subjects (pidID) are randomly assigned to three groups; the dependent variables were measured at multiple time points … Read more

## ANOVA. Let α β γ δ be regressors. If you discuss the interaction α*β*γ, can you discuss β*γ*δ too?

I’ve been taught that if you discuss an interaction of the regressors α and β, then you can’t discuss the simple effects (α alone and β alone). I guess you can’t even discuss αβ if you discussed αβγ. I wondered that maybe the rule is that in general you can’t discuss different interactions if they … Read more

## Help: What is the theory underpinning unit-treatment additivity for ANOVA

I have read extensively about the assumptions for ANOVA, and I am experiencing confusion with the concept of unit-treatment additivity. I would be deeply appreciative if anyone could please explain the theory in laymans terms. Many thanks in advance if this is possible. Here is a short excerpt from my text book The equal variance … Read more

## ANOVA – Do I use raw or aggregate mean data to compare groups

Here is my study design: there are four soil plots – A,B,C,D each plot is sampled for soil moisture at 15 locations this soil moisture sampling is done for 10 rain events I need to compare the soil plots A to D for statistical difference of soil moisture. First approach – I took an average … Read more

## Classical vs GLM aproaches for calculating two-way ANOVA

What is the main difference between the classical approach of the calculation of two-way ANOVA and the general linear model (GLM) approach? Is it possible to determine the coefficients of a general linear model from the output of the classical two-way ANOVA? The classical approach is based on the Fisher’s method. Answer AttributionSource : Link … Read more

## Is it appropriate to apply ordinal regression to a continuous response “as is” (with no ties)?

The goal is to run non-parametric general linear model with no restrictions on the design (e.g. not limited to one-way ANOVA as in Kruskal-Wallis test; quantitative factors should be admissible, etc) and to be able to estimate contrast p-values. Each observation will be converted into rank with no ties. I saw a few warnings about … Read more

## I think this is a RCB design…but I’m not sure how to analyze it

Edit: Clarified by including the overall question I need help with and the experimental questions of my project. Overall question to you (ie, what I need help with): Does this experiment sound like a Randomized Complete Block Design and if so, do you include interactions between block and fixed factors in your model (using JMP). … Read more

## whether the car::Anova function can be used for GLMM

Now, I am running a generalized linear mixed model using lme4 package. I have three category factors (factor 1 has three levels, factor 2 has two levels, factor 3 has five levels). And I want to have the main and interaction effects of them. Here is the model I built: Model <- glmer(family=binomial, data=data1, formula=value~factor1*factor2*factor3+(1|item)+(1|subject), … Read more

## What is the distribution of \$d’\$?

In my experiment, repeated measures of \$d’\$ (computed from hit and false alarm rates) are computed for a small number of subjects (<10) under multiple (10) conditions. Primarily, I am interested to see if any of the 9 out of 10 conditions differ from the control condition. I am wondering if I am supposed to … Read more

## How to you calculate the Mauchly Test by hand

I am creating a web application that is supposed to perform a Mauchly Test but i cannot find hand written or worked examples anywhere. It is imperative that the answer must not provide examples using applicatios such as SPSS or R etc as i will be doing all calculation through PHP. Would somebody be able … Read more