Analysis of Covariance. This is really a special case of multiple linear regression, used in ANOVA-like settings with some continuous covariates in addition to the categorical ones.

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multiple linear regression with factors

I am conducting a multiple regression analysis on a number of variables to determine the dependent variables. However, some of these variables are factors (have entries 1 or 0). If general ...
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Controlling for White Matter when looking at a sub-section of White Matter in the Brain - Valid Statistically?

I am interested in other people's opinion on the following matter. I have just come across a brain imaging paper that looks at differences in the volume a sub-section of white matter (SS) in the ...
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reconciling Linearity and Multicollinearity assumptions in ANCOVA

For ANCOVA, many textbooks and other resources require, among other assumptions, that covariates be linearly related to the dependent variable, which makes sense. However, many of the same sources ...
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19 views

Different results when conducting regression and ANCOVA in SPSS [closed]

I'm conducting a regression analysis with two binary categorical variables and one continuous variable as independent variables. From my understanding, the results should be identical as the results ...
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7 views

ANCOVA--Introduce second covariate

I am conducting a pretest-posttest ANCOVA with a control group in which I covary the pretest data and use the posttest data as the dependent (Jobs). Time is a repeated measure with 6 pretest and 9 ...
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12 views

Can I input a categorical variable (2 levels) as a covariate in an ANCOVA?

In my study I have two groups that were tested on different days. One of the groups received an additional behavioural test that the other did not and I want to ensure that this does not have a ...
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22 views

Why do needed sample sizes for ANCOVA versus OLS differ so much?

I am planning a study of the effect of an intervention on two groups. While computing the appropriate sample size (using GPower) for the study, I noticed that ANCOVA requires about 4x the sample as an ...
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11 views

ANCOVA not significant

How can it be explained that, when including covariates (thus performing an ANCOVA), there's no more main effect? Is it because there are other possible covariates that are not included in the ANCOVA, ...
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23 views

Non significant main effect after controlling for covariates [duplicate]

After doing a t-test that showed a significant difference, I did an ANCOVA with 3 covariates. The ANCOVA showed no significant effect of the variable that did show a significant difference in the ...
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30 views

Proper regression method for multiple continuous independent and a single continuous dependent variable?

I have 3 continuous (actually ordinal) independent variables and a single continuous dependent variable. I'm trying to sort out which regression method I should use in this case. MANOVA appears to ...
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32 views

How can I conduct a non-parametric version of MANCOVA in R?

Is it possible to transform my variables to their ranks and apply MANCOVA to the transformed data, just like how it is done in rank ANCOVA?
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12 views

Should I use repeated measures ANCOVA for single group study?

in my study I have only one treatment group (no control group), and I want to examine the changes of three DVs, so I have a pre, middle, and post surveys, and the presurvey was administered before the ...
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32 views

Can ANCOVA be used with a dichotomous dependent variable? If not, what have these authors done?

As stated above, if and how can ANCOVA be used with a dichotomous variable as the dependent/outcome variable? I found an article of which I wish to replicate some analyses ...
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Test that constant input corresponds to constant output

This may be a silly question... I have 2 times series: S1 and S2 The assumption is that the values of S2 are dependent on the values of S1. When I graph S1 and S2 for a period of time when S1 is ...
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23 views

Mixed Methods Analysis of Variance with a maximum likelihood approach

I am having trouble with a major analysis change suggested by a reviewer for my paper. I will start by stating what I did in the paper: I was interested in seeing subjective interest in two types of ...
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37 views

Equivalence of ANOVA and Linear Regression

There exist a number of resources explaining how a basic one-way ANOVA is equivalent to a linear regression model using effects coding. Interestingly, my statistics education has primarily focused ...
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21 views

Newbie question: can a categorical IV be included in ANCOVA with only a couple observations in 1 group

I think this is a pretty simple question, but I have been unable to find an appropriate answer. Please help. I have identified a sub-sample of my treatment group that were taking a medication that ...
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34 views

Covariate and DV - can they be the same?

I have two IVs (personality and teaching method) and a DV of self-esteem. I'm running a pretest/posttest ANCOVA (as I can't randomise) and am not sure if the DV and covariate can be the same. Can I ...
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20 views

adjust a non normally distributed numerical variable for a categorical covariate

Length of hospital stay was measured in 3 groups of patients (group 1,2,3) the length of stay is numerical continuous e.g. 4 days of 6 days one of the other variables is a confounder measured as a ...
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23 views

R: ANCOVA with two time points and one covariate

Consider the following experiment: Patients with epileptic seizures have blood samples taken when arriving at the hospital. Additional samples are being taken for a study of a new blood biomarker of ...
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40 views

R² of ANCOVA mostly driven by covariate

Based on data from a scenario-based experiment, I am running a 2x2x2 ANCOVA with one continous covariate (sample size=320). Without including the covariate, the ANOVA model and two of the main effects ...
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8 views

ANCOVA- Linearity with three CVs

I'm conducting an ANCOVA with a categorical IV (gender), obviously a DV and 3 CVs (one of which are also gender, but for a different group of population). I've tried assessing linearity for the three ...
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138 views

How do I understand ANCOVA in basic layman's terms?

I need assistance understanding the concept of ANCOVA in very basic layman terms. Also, can someone explain how ANOVA is different from ANCOVA: it seems both these techniques are used to compare means ...
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35 views

How to run a non-parametric ANCOVA in R?

I want to run a non-parametric ANCOVA in R and have come across the sm package and sm.ancova in R. However, I've been unable to ...
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Multiple Regression approach and ANCOVA approach to check for homogeneity of regression slopes

Hi i have a mixed design set of data with one continuous variable of satisfaction with 2 levels (pre- & post-) and one categorical variable of Service with 3 levels (S1, S2, S3). When running ...
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30 views

How to interpret a covariate in ANOVA and why are type II vs type III SS so different?

I am trying to understand the effect of a covariate (COVAR) in a linear mixed effects model with 2 categorical IVs (IV1, IV2). In order to illustrate where I am struggling, I had to paste the rather ...
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18 views

How to do ANCOVA in R

I have a plot of samples versus a number The red dots have been modelled with a red regression line and the blue dots with a blue regression line. I would like to compare the two regression slopes to ...
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22 views

ancova and logistic regression contradictions

I am seeing whether a cognitive variable fluency is significantly different between two groups and if that particular variable can also differentiate the two groups. My Group effect for fluency ...
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1answer
31 views

Determine statistical significance between linear regression

I am looking at the relationship between two variables using linear regression (Ordinary least squares method) and would like to compare this relationship between different subpopulations. How can I ...
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10 views

ANCOVA where slopes are not different

I have an observational experiment, with two groups measured before and after treatment. I'm using an ANCOVA analysis, but the assumption of independence in slopes is not met - ie the slopes are the ...
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25 views

Nonparametric Ancova with 2 covariates or PERMANOVA with covariate in R

I am having trouble determining which model to run on my data (as well as finding code to run the data). First I have 1 factor (with 3 levels), 2 dependent variables with a significant correlation ...
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60 views

Can I use change scores to analyze ordinal ratings?

I developed a re-coloring algorithm to make maps more accessible to the color vision impaired. In order to test this algorithm, I created a questionnaire in which participants answered questions ...
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27 views

How ANCOVA deals with replication?

If I have multiple observations of the dependent variable in each condition, does ancova work with that?
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95 views

how do i calculate sample size for ANCOVA?

I have two IVs and one covariate. How do i calculate my sample size. I'm not sure how to use the gpower software too. your help is greatly needed. thx.
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Is covariate adjustment appropriate in this case?

I have two conditions, A and B. In condition A, my covariate is always 0. In condition B, it is always > 0. The covariate is the number of "bonus coins", and it happens at random times (every 0-15 ...
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Covariate is related to independent variable, and also manipulated

I'm studying players inside a game. My covariate is "bonus coins". In condition A, bonus coins is always 0. In condition B, bonus coins is always > 0. Bonus coins in condition B spawn at random ...
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Can age,education level and socioeconomic status be controlled but not as covariates to strengthen an experimental study?

Most ppl include age, education level and socioeconomic status in their demographics just to show their sample of study. But in my case all those 3 factors are predictors of my DV which is prosocial ...
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Multiple Regression: 3 groups for IV, post-hoc equivalent?

I would like to test the following: DV - Brain volume IV - Participant Group (Patient with Mild Symptoms, Patient with Severe Symptoms, Controls) Covariates - Age, Gender, IQ I wish to use ...
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Do I have a justified reason to exclude a non-significant covariate from my ANCOVA? How interesting is unequal variance?

I am comparing glutamate concentrations across groups (2 groups). I planned on controlling for age and IQ, simply because this is what is always done in cognitive neuroscience. When doing this, age ...
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44 views

What analyses do I run for a 1 x IV; 2 DV's; and 2 x timepoints?

I am looking to run an analysis that has: 1 x IV (group type: control vs intrevention) 2 x DV's (Alcohol Consumption, and Modelling Behaviour) 2 x Timepoints (Baseline and 1month follow-up) I was ...
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28 views

Which statistical method can I use to see if there is a correlation between data sets with different size?

For my thesis I want to compare the 3 different test results. If the results are more than 5, samples are failed. And I want to show if these tests are similar behaviour (if there is a correlation ...
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24 views

Two-way ANCOVA with count data— Poisson model in SPSS

I am attempting to compare the number of eating episodes by gender and diagnosis (4 levels), adjusting for BMI and age. I am assuming that a Poisson model would be preferred over a factorial ANCOVA ...
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25 views

Multiple categorical and continuous variables in ANCOVA

I have performed an experiment where insects in a certain order were captured and identified at set distances from a forest boundary. At each point I have measured a number of environmental variables ...
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30 views

How to choose variables to include in ANCOVA

I have a data set that includes a DV (Richness or Abundance) and multiple continuous and categorical variables: ...
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99 views

ANCOVA without between subjects factor

this might seem like a stupid question but my knowledge of statistics has become fuzzy over the years. I would like to perform an ANCOVA without using a between subjects factor. Is that possible? I ...
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24 views

How to address unintended confounding in an experiment

I am conducting a study looking at the effects of 3 different footwear conditions on energy expenditure during running. This will be a repeated measures study. I want to control for the effects of ...
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53 views

Polynomial ANCOVA glm in R

I have a data set of success and failure counts with one continuous independent variable and one factorial variable: ...
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36 views

Comparing correlation between groups

My data looks like this: ...
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52 views

What statistical approach to use for this kind of analysis?

I have 1 dependent (continuous) variable, 3 explanatory (continuous) variables and a bunch of control variables. The explanatory variables are my interest variables.I want to do a categorical ...
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56 views

removing the effect of a categorical variable in a linear model

I would like to remove the effect of a categorical variable from a linear regression model. A simple example could be the following: outcome ~ beta0 + beta1 * dummyIsFemale + beta2 * ...