Questions tagged [anova]

ANOVA stands for ANalysis Of VAriance, a statistical model and set of procedures for comparing multiple group means. The independent variables in an ANOVA model are categorical, but an ANOVA table can be used to test continuous variables as well.

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How should I analyze data that is paired and also repeatedly measured?

I have data collected from the same subjects (n=10) over 11 days, with measurements taken under two conditions each day: immediately after training(D0) and 30 minutes after training(D30). The data is ...
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Is a correction for sphericity violation needed for post-hoc comparisons following repeated-measures ANOVA?

In a repeated-measures ANOVA, there is an assumption of sphericity, so that the variance of differences between groups is similar for all pairs of groups. A violation of this assumption can be ...
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A Priori Sample Size Needed for Linear Mixed Model

I'm new to the site so I apologize if I fail to follow some norms. I am an early-stage doc student and am still early in my stats courses. In a class, I want to propose the following experiment based ...
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multiplicity-adjustment w/ unequal variance & pre-planned vs post hoc

The (only) answer to this question says If the variability of the data in each category of your factor is non-constant, that would invalidate ... your multiplicity-adjusted post-hoc p-values. Why ...
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Relationship between f test and t -test [duplicate]

I am working on a problem where I should derive the t test statistic from an f test given an ANOVA table (below). From my understanding, when we conduct an f-test we are using the variance to ...
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How do I calculate the power and effect size for the Wald-type statistic of the RM-function from the MANOVA.RM package in R?

I have calculated the RM-function from the MANOVA.RM package in R and now need to calculate the statistical power of the test and the effect size for its Wald-type-statistic, including the ...
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Understanding how ANOVA works

Consider a one-way ANOVA consisting of two treatments 1 and 2 (argument easily extendable to multiple groups). The sum of squares within groups (SSE) is defined as $\sum\sum(X-\overline{X}_{j})^{2}$ ...
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selecting the most appropriate statistical test for comparison of multiple independent variables belonging to two groups

I want to compare the drinking water chemistry of two areas. A disease is prevalent in one area while the other area is almost free from this disease. I have measured the concentrations of 10 ...
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Statistical approach to explain variance in different types of soil health data (organic material decomp vs lab based measures)

Seeking feedback and guidance on the statistical approach to explain variance in soil health data for a scientific paper on the sensitivity of organic material (teabag) decomposition to commonly used ...
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How can I test if lower values on my regression line come from a level of a grouping variable?

If I have continuous x and y variables I can fit a simple regression. But I want to know how can I test if the lower and upper values of my variables are associated with different groups as in the ...
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Appropriate way to correct for multiple hypotheses with multiple one-way ANOVAs and Tukey's post-hoc

I have a dataset with four groups and 14 different dependent variables. Based on the answer given here, I think the best approach for my analytical question is to perform multiple one-way ANOVAs, ...
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Non-parametric ANCOVA post hoc test

I am doing a non-parametric ANCOVA (my residuals are not normally distributed and transformation did not help), I have been using the sm.ancova function from the sm package in R. Now I want to do a ...
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Does a 2x2 study mean there are 4 groups or 2?

My study is a 2x2 design. There are 2 IVs: IV1 = sex (m/f) ; IV2 = control / experimental groups. Does this mean that I have 2 groups, and will therefore be using an independent T-Test, or i have 4 ...
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Is there a statistical test where you test whether any of multiple separate analyses of variances or chi-square tests are statistically significant?

Is there a statistical test where you test whether any of multiple separate analyses of variances or chi-square tests are statistically significant?
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Compairing two groups with paired data

I have two groups of samples: healthy and diseased groups. Each had an X treatment. So, I have a healthy baseline and healthy X treatment. The same for the disease group. Which is the best way to ...
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Why does removing the offset change the F-statistic of an anova model in R?

When a linear model with only a single categorical variables is defined without an offset, the F-statistic reported by summary() and ...
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Is repeated measures ANOVA suit my method

I use a randomized, double-blind, placebo-controlled crossover method. Participants visit 4 times. 1 time for placebo at sea level, 1 time for placebo at hypoxia room, 1 time for beetroot at sea level,...
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plotting log-transformed data, but running statistics on raw data?

I intend to compare differences between means of eight groups. The differences between some of the means are only visible when I plot (in a box plot) the log-transformed data. However, I am unsure as ...
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Formulas for type I, II, and III SS in R's car::Anova()

In the Anova() function of the car package one can specify whether the ANOVA should use type I, II, or III sum of squares to ...
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Intuition of F statistic calculations in 2-way random effects-, fixed effects- and mixed effects-ANOVA

I try to understand the logic behind the math of random, fixed and mixed effect models. So far I think I've understood that they are all based on the same mathematical model, e.g. $Y_{ijk} = µ + \...
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Is correction for multiple comparisons necessary in this instance (single variable)?

Coming here from a more analytical chemistry background, but I figured I would run my current thoughts here before committing to anything after looking around for a bit. I'm used to always using ...
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ANOVA Type (1 v 2 v 3) for Mixed ANOVA

I know things related to this question have been posted before, but they don't answer my specific situation. Additionally I've consulted with the university statistician and been unable to get an ...
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I know this is a very basic question but I am new to statistics [closed]

How would you approach analysis of 6 groups representing a range of values, increasing in value against a continuous variable (number) ? I am learning to use R right now. Would I have to use ANOVA? ...
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Full Factorial Designs and Honest Tukey

I am trying to analyze the data of a 2x2x2x2 full factorial design experiment. (It wasn't my idea.) Mercifully, we have plenty of data per run, each run has the same amount of data, and normality and ...
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Necessary normality assumptions for a one-way ANOVA

I am wondering about the normality assumption. It is required because underneat all this, ANOVA is running a F test. The denominator of the F test is the sd of the residuals, thus we need these ...
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Proportion testing from pooled single cell/nucleus samples

I have a snRNAseq experiment with a 2x2 layout (wt vs transgenic, drug vs vehicle; Wt-V, Wt-D, Tg-V, Tg-D). I have 6 mice per group, but for cost reasons we pooled pairs of samples in each group, for ...
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Test for significant difference between two groups measured across time

I have two groups of time-dependent samples whose measured value changes nonlinearly with time. There are 3 samples in group A and 3 samples in group B. An example of my data is illustrated below. ...
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How do you interpret the results of an anova(model)?

This seems like a simple question, so apologies if it is already repeated elsewhere (though I could not find the answer when I searched for it). I coded a linear mixed effects model as follows using R:...
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Repeated measures ANOVA on proportion success or logistic multiple regression on total binary data?

I have 24 subjects. I have measured distance displaced between image frames at a framerate of 1Hz, so how far did the subject move in a 1sec interval? The continuous movement variable contains many ...
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How does type II vs type III ANOVA work when there are more than two categorical predictors?

For a model with two categorical factors in the form: X = A + B Type I (used if the factors are balanced) calculates SS for each term in the model sequentially as follows: SS(A) then SS(B|A) = SS(A ...
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I would like to perform a Kruskal-Wallis test in Jamovi [closed]

My problem is that I have data of sexual assertiveness (7 point Likert-scale, SAQ) and relationship satisfaction (5 point Likert-scale, RAS) but I would like to divide the sexual assertiveness ...
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Why the Sum of Squares Error in ANOVA has n-1 degrees of freedom?

There is a statement that got my attention recently, which is "ANOVA is just linear regression". I was watching this video that seemed to explain the relationship between the two topics. At ...
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DiD vs Repeated meausres ANOVA vs ANCOVA

I am learning statistical analyses for experimental and quasi-experimental studies. From my class and by searching answers here and asking ChatGPT, I have some preliminary understandings of Difference-...
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Which of these is the correct way to encode a type III ANOVA analysis?

I am trying to run a type III ANOVA analysis to look at how the three factors A, B and C affect the continuous variable X. Online I have found two ways of encoding the model which give different ...
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Am I using emmeans correctly to look at pairwise differences after running a type III ANOVA model?

I am looking at how the weight of female individuals is influenced by the two factors A (5 levels) and B (2 levels) using a type III ANOVA as follows: ...
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mixed effects model when within group variance cannot be estimated

What is a mixed effects model when the within group variance cannot be estimated. For example I have an outcome that is very rare to begin with. Less than 5% of children have this outcome. Then I have ...
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An contradictory negative edge

Recently I have conducted a experiment exploring the relationship between stress and mind wandering (MW). When I analyzed the data via SPSS, I found an unexpected negative edge between two variables. ...
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Query re Normal Distribution of Data for GLM [duplicate]

Ive collected data for force measurements (response variable) based on 3 factors in unique tests material type (2 off) (I assume this is categorical) tool radius (2 off) (assume this is discrete as ...
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Repeated Measures & Standar Error of Measurement (SEM)

Single subject study test force with: 2 Devices simultaneasly (A and B) 5 differents positions (s1,s2,s3,s4 and s5). 2 differents rooms (Y and Z) Repeat each position 6 times consecutly. Different ...
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Two-way ANOVA help

I am measuring the differences in fungal abundance in different stages of grazing and depth so I have tow factors (grazing intensity and soil depth) My main effects are all significant but so is the ...
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What statistical analysis test can be used to find the direction of effect?

I'm doing research on the effect of strategic video game play on students' mathematical ability. My independent variable is the number of hours spent playing strategic games daily, but my data is not ...
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Significant interaction when only one of the two main effects is significant? [duplicate]

I have run a mixed effect logistic regression model, and I have obtained a significant main effect of Factor A, while no significant main effect of Factor B. However, the interaction between Factor A ...
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What statistical analysis method should I use for two independent variables with interval data and a dependent variable with continuous data?

I'm doing a study on the potential of date leaf ash and date fruit seeds as replacement materials for cement and sand, respectively. For date leaf ash (DLA), there is 0% replacement and 5% replacement,...
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Computing Type 3 Sum of Squares of AN(C)OVA

I have a two-way ANCOVA model of the form $$y_{ijk} = \mu + \alpha_i +\beta_j+\gamma_{ij}+\delta c_{ijk} + \epsilon_{ijk}.$$ Rewriting this model in matrix notation gives $$\boldsymbol y = \boldsymbol ...
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How to do ANOVA/post-hoc analysis when 'control' is used to normalise the data?

I am analysing the transportation rate for a number of different mutants in a particular transportation system. I want to know how I can perform statistical tests on this data in a valid way, given ...
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anova_lm function for a single multiple linear regression model [duplicate]

When using anova_lm from statsmodels with a single multiple linear regression model, how are statistics for each predictor calculated ? E.g. ...
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What really happens if I run Tukey without running ANOVA first?

I see that the theory says that if I want to test for difference in mean between 3+ groups I should use ANOVA first, and if ANOVA rejects the null hypothesis then I might want to look into Tukey as a ...
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Analyzing data with multiple treatment layers

I apologize if this is a silly question, but I'm having some trouble figuring out the best way to approach analyzing my data. I have a study where we investigated the effects of different dietary ...
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Analyzing binary data with repeated measures across different levels in R

I have this data frame: https://i.stack.imgur.com/EGh1z.png It is the binary recorded responses (repeated measures) of subjects to 4 different tests under 2 environmental conditions (2x4 factorial ...
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What if anything is being fit in a one-sample t-test?

I am revisiting some basic concepts involving t-tests and ANOVAs, and got tripped up early. I wanted to apply the concept of lack-of-fit sum of squares to the single sample t-test but wonder how this ...
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