Statistical Analysis Stack Exchange
Statistical Analysis Stack Exchange

Questions tagged [ancova]

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.

ANCOVA is used in ANOVA-like settings to control for any independent variable, which although not of interest, may affect the relationship between the dependent variable and other variables in the model. For example, to test the effect of asbestos on lung cancer, smoking would be included as a covariate.

ANCOVA is not substantively different from the General Linear Model: the term 'ANCOVA' may be used when a predictor of interest is categorical and it is wished to control for the effects of one or more continuous predictors; the sums of squares for the former are examined after partialing out those for the latter.

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ANCOVA with repeating covariate

I wonder if someone can help me with an ANCOVA covariate question? Perhaps you may know the answer to my problem. Subjects were assigned to a treatment or control group, and I measured a (continuous) dependent variable. There is also a covariate,…
david
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Ancova when covariate is of theoretical interest

My experimental design contains a repeated-measures, categorical variable (three levels, type of sentence) and two continuous predictor variables (two subscales scores derived from a questionnaire). The design is balanced and meets assumptions of…
Elizabeth
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Requirements to perform a two-way factorial ANCOVA

This is a question that landed on my desk, and I don't have the requisite experience to reply. A researcher has been asked to perform (by a journal reviewer) a two-way factorial ANCOVA on some microrarray data (a single array will be a single…
user133
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Interaction in ANCOVA

I'm doing a study with frogs in which I see that there are differences in jumping ability between juveniles and adults, I get that adults jump more than juveniles. I want to check if these differences are really due to the fact that there is an…
Mr.Frog
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choose between ancova model and one-way anova

Let's say that I want to know three training program effectiveness. Our independent variable is categorical variable (with three levels). Our response variable is after-train scores. Then I introduce a co-variate variable: before-training scores. I…
ElleryL
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How to test for homogeneity of regression slopes

How do I test for homogeneity of regression slopes in ANCOVA? I really need some conceptual and practical help with this assumption. I've scoured the web but a lot of them are not too helpful. Also ideally I would like to be able to test this…
Sarah
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Ancova Levene's test significant

I did ANCOVA with Depended: Posttest/ Fixed: Group/ Covariate: pretest Levene's test is statistically significant: .002 Is the assumption of homogeneity of variance violated? If yes , what can i do about it? I am asking since I had done it with…
Bernard
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Correlation between dependent variable and the covariate in an ANCOVA

I want to check the effect that a categorical between-subjects factor A and a continuous predictor B has on a certain dep. variable. I created an ANCOVA with A as a factor and B as a covariate. This should tell me whether there is a main effect of A…
z8080
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Can you put more than one factor in ANCOVA analysis?

I am running ANCOVA on SPSS using post-operation score (continuous) as Dependent variable, pre-operation score (continuous) as Covariate, and 2 groups (categorial 1&0) as Fixed factors. This is the usual scenario. But can I add another 2 variables…
Emaddin Kidher
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Including a baseline measure of the DV as a covariate in an ANCOVA

I have 4 groups based on BPD symptoms at baseline and follow-up. (BPD T1 and T2; BPD T1 not T2; no BPD T1 but BPD T2; Never BPD). I am examining whether psychosocial functioning outcomes (SOFAS score) differ amongst the groups. As I wish to control…
Sarah
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Nonlinear dependence on continuous variable: alternative to ancova?

I have data that looks something like this: I was hoping to run ancova, but the data is not linear in the continuous variable, and there isn't an obvious transform to apply. However, each group is roughly a shifted version of the other (I have…
neuronet
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Difference between ANCOVA and Randomized Block ANOVA

What is the difference between an ANCOVA and a Randomized Block ANOVA?
Ann-Marie Castille
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ANCOVA: How does a covariate give insight when comparing the mean to the adjusted mean?

When comparing the direction and magnitude of the difference between the original means and the adjusted means what does the change say about the covariate? For example: IV = Grade, DV = Test Score, Covariate = IQ Score Am I correct in assuming that…
Arctic
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Choosing the best analysis

I need to do a data analysis in R. My data consists of 2 populations of animals that have 2 different types of genomes. The children are always born as twins. I also know the mothers' weight and the combined weight of the children after 14 days. I…
Kadri
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Dummy Coding ANCOVA in spss

Scenario: 1 continuous DV = problem solving ability 1 categorical IV = exposure, no exposure 1 categorical covariate = previous preference (like, dislike, neutral) How do I dummy code the covariate in spss? I don't want to perform a regression…
IKA
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