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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.

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When to include covariates when I hypothesize there's a difference between groups?

If I am hypothesizing that there is gender difference in a certain domain, and that another variable would moderate the gender difference, should I include covariates in the analysis? The key of this ...
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p-value of Covariate differs between Regression and ANCOVA

I'm using SPSS to run a regression analysis in order to predict navigational performance (continuous dependent variable) from self-assessment scores (continuous predictor), sex and age group (both ...
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Centering covariates with repeated measures ANCOVA

I have a study design with a repeated measures variable (four time points) and a time-invariant covariate. I am analyzing the data using a repeated measures ANCOVA in SPSS. I am interested in the ...
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I made a one way ANOVA with a covariate on spss, how can i represent the results graphically? [on hold]

My question is about ANCOVA. I did two univariate analisys of variance, with a covariate. I want to represent my result graphically, but I have no idea how to do this. Can I do a scatterplot or I ...
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Valid use of repeated measures ANCOVA

I am running a repeated measures study with four time points. A single group of participants receive the same questionnaire at each time point, which is assessing variable X. I am determining how ...
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How to statistically compare feature sets with different levels of data collapsing over category and training splits?

Background: As part of my research into image classification from small numbers of examples: I created 4 disjoint feature sets by extracting activations from different layers of a deep neural network ...
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Test to compare on an ordinal scale, two groups of data that have covariates

I have two (Test and Control) groups of data. Data in each group is divided into 10 (ordinal) period. In each of these periods, number of observation ranges anywhere from 22-53. The assumption is that ...
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Step-wise Multiple Regression or ANCOVA

I have an assignment that gives a dataset and a choice of 3 tests: Step-wise Multiple Regression, ANCOVA and Log-Linear Analysis. The dataset consists of ...
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Hypotheses check with mixed ANOVA, ANCOVA, regression or multilevel linear model?

I conducted a repeated-measures experiment and obtained for each subject the following data: ...
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What post-hoc analysis should I use following a two-way ANCOVA with factor, integer and numeric variables?

I ran a two-way ANCOVA on the data below, in r-studio, to determine whether pupal weights Pupal.wt were affected by caterpillars' diet ...
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Trying to find whether a categorical (gender) and numeric variable (heart rate) differ between each other while controlling for Age

so I tried to use ANCOVA in R and when I was doing the diagnostics test, turns out the data is not normalized. Now I am stuck, and I do not know where to go from here. Please help. Is there a way that ...
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ANCOVA vs Random effect for category

Assuming a categorical variable is a nuisance variable, why would one ever use it as a fixed effect as in ANCOVA instead of using it as a random effect? As an example consider modeling the ...
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GPower Sample Size Error with Large ANCOVA Model

I am trying to do a power calculation that with a very large ANCOVA model but am getting an error because my number of groups is too large. I have 14 binary variables, two 4 factor variables, a 5 ...
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Two Way ANOVA or ANCOVA?

I have three groups, one control, one having high fat diet and one having high fat diet+treatment and i want to measure the concentration of glucose over a period of time in these groups. Should I use ...
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Does reversing a covariate change the within-subject effect in a repeated measures ANOVA? Why?

I noticed I coded a variable in the wrong direction, so I reversed it. I thought this reverse would not matter for drawing inferences from the ANOVA analyses (e.g., p-values or effect sizes) as there ...
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What to do when there is heteroskedasticity in an ANCOVA model?

What to do when there is heteroskedasticity in an ANCOVA model? Is there a correction similar to Welch ANOVA? Or is better to use a OLS regression model? Should we try to solve heteroskedasticity by ...
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Is ANCOVA suitable/scientifically sound for my case?

I have a question regarding the suitability of co-variate. I have three groups with different levels of production in pcs (low, medium, high), material waste in % and number of machine setup changes. ...
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How to calcualte confidence interval for the residual variance in ANCOVA models

As the question states I need to know how to calculate this. Given variable $Y$ and $X$ with $\operatorname{cor}(Y,x)=r$, the residual variance is: $$(1-r^2)\cdot\sigma_Y^2,$$ which represents the ...
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merit of t-test vs repeated measures

In a cohort study, patients have been enrolled for a new method of treatment of a condition. The measurement of interest, for example, tumour size is taken at baseline (BL) ie before treatment, the ...
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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 ...
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Statistical analysis techniques for pre and post repeated measures

I am trying to understand which is the appropriate statistical technique to use for the below experimental design: Design: I have two groups - an intervention group (that took an action, eg increased ...
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Analysing pre and post treatment within one group plus two control groups

Basically, I have a mixed design, with 3 groups (between subjects), and 13 personality traits (within subjects). However, one of the groups has pre- and post- scores. There was a fictional character ...
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Comparing the results of 2 different type but identical samples from 2 devices

I have 2 columns of of the concentration of fat in fish which is measured by 2 different labs. I need to know if the difference of the results from these 2 labs are statistically significant. The data ...
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ANCOVA multiple confounding continuous variables

I want to perform an ANCOVA analysis to test whether mpg shows differences between a categorical variable am; together I want ...
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Significant main effects lost during ANCOVA due to interaction terms. Is type III the way to go?

I have some experimental data which I am analysing using step wise multiple regression (ANCOVA) in R using the step function. The response data (wp) is the leaf ...
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Interaction between covariate and 2-level within-subjects factor is of research interest. How to test

I'm interested in interpreting the interaction between a continuous variable (C) with a dichotomous within-persons factor (A) on a continuous DV (DV). What is the best overall test of this? Would it ...
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Can I do it through Repeated Measures ANCOVA? If so, how can I interpret the results?

I'd like to have some help, please. I'm writing my masters and I have a huge doubt about which test should I use. What I want to measure is: the effect of therapy on people who have and don't have ...
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What statistical tests should I use for this between-subject user study?

So, I have performed a between subject experiment, where half of the users used Tool A to perform the Task and the other half used Tool B to perform the Task. Each tool had specific mechanics to ...
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ANCOVA - Non-linearity of covariate

I have a dataset where I calculated genetic distances between populations of some animals (a continuous variable). I want to know if these differences are explained by physical or/and ecological ...
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how to handle overlapping numerical data in an ANCOVA

I am a graduate student in psychology and am trying to understand the best way to conduct an analysis. Here's a short description of what I want to do: I transcribed the speech that participants ...
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How do I perform an ANCOVA ? (master thesis deadline) [closed]

My dataset consists of several morphological measurements for 5 island populations of a certain lizard species. I want to test for each population if there is a significant difference in the ...
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CFA - longitudinal experimental data

I have an experiment (control & experimental group) with an intervention. There are pre- and post-tests and then another post-test 1 year later. I have 3 measures for each of 3 theoretical ...
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Covariates and moderator variables

I have a 4 * 3 (both the IVs are categorical) factorial design with two covariates (both are continuous) to run ANCOVA. Can I do a moderation analysis?
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Time series regression

I have a dataset of SO4 concentration (annually) from 1986-2016 across 35 water catchment stations. The dataset looks like this: I first plotted the data and found out that the trend pattern is ...
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Further analysis of significant interaction between a covariate and independent variable

I am studying to see if there are differences in mussel feeding ability (CR) based on 10 different food types (Taxa) and water source (Treatment) using the covariates shell length (SL) and Initial ...
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Comparing Multi-Year Survey Data (Is Repeated Measures ANOVA appropriate?)

I have a question which requires your helpful expertise. I am conducting a survey which, through the utilization of a scaled response from participants (1-10), measures for significance in ...
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Follow up for interaction from Repeated Measures ANCOVA

I'm writing a paper which uses a 2x2x3 repeated measures ANOVA in SPSS. My dependent variable is reaction time and my repeated IVs are different visual conditions. I have a continuous between subjects ...
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Cohen's d from a linear regression model

Problem: I have a multiple regression model with categorical/binary ($c_i$) and continuous ($x_i$) variables: $ v = \alpha + \beta_1 x_1 + \beta_2 x_2 + ... + \gamma_1 c_1 + \gamma_2 c_2 + $ I am ...
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Comparing different regression lines as their slopes are equal or not

I have a 4-set of time series data and each dataset has a response and its recorded date as a decimal year. For instance, there is a dataset from 2002 to 2013 having 200 data points, each data point ...
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Likert Scales as a Covariate in ANCOVA

I have a 1-7 scale on health intent and I just want to clarify if I can use this scale as a covariate in an 2x2x2 ANCOVA. I know there is contention on whether these scales are categorical or ...
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Dummy-variable regression with a binary covariate having unequal variance (violation of homoscedasticitycan)

I have a dataset (N = 158) and the following variables that I am going to put into a regression model: Y (a continuous dependent variable) X (a continuous predictor) Z (a continuous predictor) GENDER ...
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How may I estimate means and SE for an ANCOVA model fitted on multiply imputeted data with mice?

As I have incomplete data I used mice() for multiply impute missing data and then I want to perform an ANCOVA. In the end what I want to get is the means and ...
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Difference between two-way ANOVA, factorial ANOVA and ANCOVA: as analogies of linear regression

I learnt linear regression before I was introduced to ANOVA/ANCOVA. It helped my understanding to think of one-way ANOVA and ANCOVA using analogies in linear regression. Can you help me understand ...
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Can you analysis likert scale data with ANCOVA? what are the alternative when Kruskal-wallis is also not appropriate

We have conducted a trial with 30 participants, each participant given different intervention (Intervention A, Intervention B and Intervention C). The aim of the study is to compare the effectiveness ...
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Satisfying assumptions of ANCOVA

I am working through my data using Andy Field's Discovering Statistics through R. I would like to run a ANCOVA using weight at baseline as one of the covariates. This is what my data looks like <...
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using a covariate in within-subect only rm ANOVA

For a study, when I do a rmANOVA with one within-subject factor with two levels, I see a huge effect: partial eta squared is even .55 (!). Then, when I enter a covariate, the effect all but ...
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Can you remove a factor from your model if it has a significant effect, but the removal improves AIC and R square?

I have a complex problem but the title sums it up pretty easily. I have four types of cages that manipulate water flow, but I also have an actual measure of water flow from inside the cages. I'm ...
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Go with the original ANOVA or the unexpected (but welcome) ANCOVA? (Or: can I use this as an independent variable?)

I designed my experiment in a way that I thought would present me with options for analysis, but I'm starting to wonder if one of the options would be considered pseudoreplication. The experiment was ...
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Does this analysis commit pseudoreplication?

I designed my experiment in a way that I thought would present me with options for analysis, but I'm starting to wonder if one of the options would be considered pseudoreplication. The experiment was ...