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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Can I 'double' dip into a baseline to both reduce variance, and use it as a level of my with factor of time?

I have a bit of a situation I would like some advice on. I'm currently running a human subjects study where I have two groups (group 1 and group 2), and three time points. Each subject performs a ...
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ANCOVA sensitivity to large variation existing in only one of the groups

I plan to run ANCOVA to test the effect of diet intervention across 3 groups. I have before and after intervention measurements and use before measurements as covariate ( ...
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Nonlinear relation between two variables as affected by two interacting treatments

I experimentally tested the relation between dependent variable y (continuous) and independent variable x (continuous) for 6 replicates x 2 genotypes (categorical) x 3 species (categorical) each (= ...
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ANOVA, ANCOVA, linear mixed effect model

I experimentally tested the relation between dependent variable $y$ (continuous) and independent variable $x$ (continuous) for $10$ replicates of $2$ plant varieties (categorical) of $3$ species (...
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How do I calculate effect size in a pretest-posttest three group randomized study for two planned contrasts (ANCOVA)?

I am having a hard time calculating the individual effect sizes for ANCOVA simple contrasts ($1$ vs. $2$ and $1$ vs. $3$) in a randomized pretest-posttest design study with three groups. In the ANCOVA,...
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Which test should be used for an ordinal dependent variable with pretest-posttest and two factors?

Consider a pretest-posttest design, where the dependent variable (y) is measured by 3 ordinal values 1,2,3. There are also two factors: One factor (say A) consists of a control and an experimental ...
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Is Multiple Comparison Correction necessary for multiple ANCOVA tests

I'm working on fMRI data comparing brain activation from ten different brain areas across three groups after controlling for covariates such as age, sex, disease severity. I built an ANCOVA model with ...
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Power analysis for a quasi-experimental factorial design 3(manipulated) x 1 (measured) ANCOVA

I'm experiencing an hard time looking for the proper analysis to use to compute the power for an experiment i'd like to implement, so here is my question for you. I'd like to run a quasi-experimental ...
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How can I compare the results of two lmRob() models? [closed]

I am looking for a way to compare the results from two lmRob() functions statistically. Would that be a possible option for me: lmrob_female <- robust::lmRob(Y ~ X_binary + covariate1 + covariate2 +...
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Doubt on non-parametric ANCOVA with two groups and pre-post scores and pre scores (baseline) as covariate

I have used a non parametric ANCOVA to analyze scores of a questionnaire (BSCS) with factors: Type of intervention(A and B) and timepoint (pre- and post) as well as baseline (same distribution as pre-)...
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How to get an overall P-value for a categorical variable, If I know the t-values of its dummy variables?

I am doing ANCOVA: main categorical variable for the comparison is "Street" and it contains 3 categories (Street1, Street2 and Street3). The outcome variable is social interaction time (...
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ANOVA/ANCOVA results in SPSS

I am unsure about how to interpret the output box I get doing an ANOVA in SPSS. That's the "Tests of between-subject effects" box in particular. I had 2 groups (A and B), and 2 results (...
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Repeated Measures ANOVA with two covariates

I am doing a repeated measures Anova My variables are like this: Y - continues variable measured pre and post intervention Intervention - the between group variable with three levels in which ...
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Statistical analysis on cortisol reactivity (longitudinal)

I collected stress data (cortisol reactivity) on 4 timepoints. I also collected psychological measures at 1 timepoint. I would like to know if the psychological measure (one measurement time point) is ...
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Homogeneity of regression slopes and collinearly of covariates in ANCOVA (specific)

Thank you for such a great website for statistics learners, I am currently studying a factorial ANCOVA and have two questions: do we need to test homogeneity of regression slopes for an interaction ...
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Repeated Measures Ancova In R

I apologize if I am not being very clear, I have basic knowledge in statistics! I am trying to analyse my data but I am unsure if repeated measures ancova is the way to go. I have a variable named &...
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Repeated measures Ancova in R

I am trying to analyse my data but I am unsure if repeated measures ancova is the way to go. I have a variable named "A" measured in three different conditions "1", "2" ...
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How to calculate slope and linear regression in R

After creating the plot using: ...
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Can I add more than 2 independent groups to an Ancova and if so, do I need to create dummy variables in SPSS

I want to analyze the difference between 4 groups on one dependent variable while controlling for my covariate, age, and 3 different independent variables (sex, cancer type, metastasis) in SPSS. Can I ...
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Interpretation of ANCOVA output

I am struggling to interpret my ANCOVA output - I have looked at similar questions and can't figure it out. I am looking to determine whether there are gender differences in the impact of a specified ...
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ANCOVA in within-subject design

I have two questions regarding an ANCOVA analysis in SPSS in a within-subject (i.e., repeated measures) design (e.g., an experiment with 3 measurement timepoints): when checking ANCOVA assumptions, ...
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Doubt on checking linearity assumption in a mixed-ANCOVA design

I am a PhD student and I have to run a mixed-ANCOVA on some questionnaire scores (my dependent variable) according to the following model. Factors of ANCOVA are (a) Timepoint (pre-intervention, post-...
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Normalised versus true racing times as DV for a learning experiment?

I have a question about using ratios as variables in alpine ski racing research. We want to compare skiers' performance on different days, but snow conditions affect the results. To address this, we ...
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How to analyze nested data of repeated measurements? ANCOVA or linear mixed model?

I have obtained a dataset from a psychological experiment. In the experiment, each subject completed four sessions of tasks on four different days. Each session consisted of two stages of tasks. ...
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How should I proceed with a one-way ANOVA if homogeneity of variance is violated, I have unequal sample sizes, and I want to control for covariates?

I'm using SPSS. I have a multi-level categorical IV and a few continuous DV's. My main analysis goals are to test the effect of the IV on the DV, and then to follow-up with pairwise comparisons of ...
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What to do after violation of homogeneity of regression in ANCOVA

I wanted to run an ANCOVA. My independent variable is field of study (3 groups: science, humanities, and business). My dependent variable is IQ measured on a continuous scale. There are two covariates:...
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How to properly include covariates in a one-way repeated measures ANCOVA? What do results tell me?

I want to test the effect of a suicide prevention film on help-seeking. I have help-seeking intentions as an outcome variable and measured this variable at three time points (pre, post, follow-up) in ...
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An ANCOVA pre-post framework for multilevel data?

I have a continuous outcome/dependent variable that is measured multiple times before and after an treatment/intervention per subject. The multiple measures are performed very closely together and are ...
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Interpreting the output of an ANCOVA as regards to the descriptive statistics

I'm quite annoyed by the outputs of one my analyses. I'm conducting a repeated measures ANCOVA including two IVs, one DV, and two covariates. My issue is that when I include my two covariates, the ...
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What statistical test should be used for pre/post data (that violate ANCOVA assumptions)?

I want to assess the effect of a treatment (control vs. ash) on a continuous variable (e.g. calcium concentrations). I have two additional grouping variables that are also both categorical: location (...
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Extending ANCOVA for multiple timepoints

I am trying to use a repeated measures ANCOVA to look at differences over time between groups in SPSS. I was following this helpful thread (What is the correct way to add and analyse covariates in a ...
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What is the formula for the expected variance from a randomised clinical trial with a single continuous covariate

I'm reading Stephen Senn's book, Statistical Issues in Drug Development, and come across this formula for the expected variance of a randomised clinical trial, with a fitted single continuous ...
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Choosing the best and more useful method in RCT psychology studies

I'm not sure had anyone open this question but I'd like to your opinions. When we compare two groups(control&treatment) measured at pre,post and a follow up procedure, which is the most useful ...
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How to build a mixed-ANCOVA-model with lme()?

I want to perform a split-plot ANCOVA in R. I try to test, whether the assignment to one group (of two; between-subject factor) has an effect on a performance task (measured 5 times during the ...
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Which is the correct way to deal with insignificant main effect of Group condition? Stick with interaction effect in RM-Anova or perform ANCOVA?

I wanted to ask conceptual about what to do with main effects? Assume, I have randomly assigned equal two groups(let's say CBT, Control; N1=25; N2:25). I collected the depression levels at three time ...
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Can I use MANCOVA and SEM?

My project model includes one input variable, two mediators (both measured at the individual level, but one is about the team so rWG will be calculated), one moderator, and two outcome variables (...
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Validity of ANCOVA for Linear Models with Different Slopes

Does ANCOVA require homogeneity of regression slopes? In other words, do the slopes of the lines need to be the same in order to use this method? Per this blog post ANCOVA can be used to discriminate ...
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ANCOVA controlling for a categorical manipulated factor

I have an experiment where 6 subjects performed 20 different lifting tasks LT with 3 different knee braces KB. The emg activity <...
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Inconsistency in ANCOVA results between rstatix and car

I am trying to run an ANCOVA in R with a binary treatment variable, a continuous covariate, and their interaction (response ~ cont*bin). My understanding has always been that AN(C)OVA and regression ...
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Unsure of what analysis to use. Sample is too small for ANCOVA

I am trying to analyze some preliminary data for a conference. I currently have two animal participants completing a series of tasks. The tasks use different types of feedback (4 levels), which vary ...
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linear regression vs anova or ancova in clinical trial

I analyze clinical research data, This is a comparison of two treatment groups. The outcome is a continuous variable. We decided to adjust on predictors of outcome in imbalace, in posthoc (We assume ...
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What formula does SPSS apply to the data in an ANCOVA? Or exactly *how* does ANCOVA adjust the dependent variable?

The procedure for an ANOVA is really straightforward; you compute the between group variance and the within group variance, divide your results to get an F statistic, and compare it to your critical ...
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Advantages of MLM over repeated measures ANCOVA?

Hello StackExchange community! My study group and I (M.Sc. in psychology) are currently studying for an upcoming exam and can´t figure out the correct answer to the question below. Its neither ...
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Design of a Dental RCT in Which Patients Can Act as Their Own Control

I've been asked to help determine the design of an RCT. The design is primarily interested in the benefit of using a laser on some dental procedure in addition to a local anti-biotic and scaling, ...
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Calculating effect sizes for individual post hoc comparisons in ANCOVA

I ran ANCOVA with dependent variable IQ, independent variable field of study (3 groups: science, humanities, business), and two covariates (age and sex). I see that my result is significant (i.e., ...
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Question about running Quade's test instead of ANCOVA

Hypothetical scenario. Let's say I'm running 6 separate ANCOVAs. My independent variable in each is field of study (3 groups: science, humanities, and business). For each ANCOVA my dependent variable ...
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Question about linearity assumption in ANCOVA

I'm running ANCOVA. My dependent variable is is IQ, and one of my covariates is sex. I know that to perform ANCOVA you should be thinking that there exists a linear relationship between your dependent ...
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How to interpret scatterplot to test linearity b/w covariate and DV?

I'm doing an ANCOVA on a fictitious dataset of math test results (DV) by group (n1 = 50 online training; n2 = 50 no training) with previous math ability as a (covariate) to see if there is a ...
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ANCOVA analysis

I'd like to perform an ANCOVA analysis for my study. The following features: 3 groups and 1 DV (continuous) ANOVA and post hoc analyses showed a statistically significant differences There are some ...
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Between subject design, spread over multiple days

We have a between subjects design, testing for the impact of aesthetics on occupant satisfaction. Intervention is carpets vs no carpets. The people participating in each leg (intervention vs control) ...
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