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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Adjusting for age and gender in ANOVA

I am performing an ANOVA to compare the means of three groups. However, I need to adjust for the effects of age and gender in the ANOVA. I'm not quite sure how to go about it in R. Conventionally, I ...
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+100

Model suggestion for zero-bounded dependent variable

I have a repeated measures dataset (8 measurements) with three experimental groups (Randomly generated). The dependent variable (Y) is on a continuous scale bounded inferiorly at 0. I am trying to ...
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Nested factorial design for three factors

I want to design an experiment with three factors. Factor 1 shall have two levels (say, A and B), factor 2 has two levels (say, C and D) and factor 3 has two levels (say, E and F). By design, factor 2 ...
4 votes
1 answer
270 views

Only interested in select pairwise comparisons - Do I need to run an ANOVA first?

I have data with two biological factors. The first factor has 2 levels (say, Alive vs. Dead) and the second factor has 80 levels (protein of interest). I'm only interested in whether the mean value ...
4 votes
1 answer
58 views

Three versions of the independent two sample t-test (and R)

This post concerns three versions of the independent two sample t-test: Student's t-test uses a pooled standard deviation in the denominator (all equations are shamelessly copied from Wikipedia - ...
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Unbalanced Anova

I have an unbalanced 2 by 3 between-subjects ANOVA that I am doing as a regression. I'm using Helmert coefficients to code A and B, and the products of these to code the AB interaction. Because the ...
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1 answer
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R: Post-hoc tests after ANOVA on mixed linear model give different results, why and how to proceed?

I want to perform an ANOVA test on a mixed linear model. I have variable response "CK" measured in 2 independant conditions: -2 groups of horses (independant variable : Groupe: Groupe 1 and ...
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What approach would you recommend to find the dependent variables that are most affected by the predictors in a multivariate analysis?

I used to handle most of the time species count data. The approach in my group was to do a multivariate analysis of variance, and if there were many dependent variables, we tried to find the ones ...
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Dropping a condition in a 2 way anova on apex aov_ez

Trying to replicate analysis of a paper. They use 2 way anova with 3x3 design. Except one condition (one cell in the anova matrix) never happens. They specifically say that they use 8 conditions in ...
-1 votes
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Are the variances in a F-test in Analysis of Variance "nuisance parameters?"

ANOVA estimates 3 sample variances: a total variance based on all the observation deviations from the grand mean, an error variance based on all the observation deviations from their appropriate ...
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+50

How to summarise ANOVA post-hoc Tukey test?

I am having trouble to interpret tukey's post hoc result from the following They incorporated post-hoc test results into a table using the π‘Žβ‰€π‘<𝑐 style notation (π‘Ž,𝑏,𝑐,... correspond to ...
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Do there exist welch's repeated measures anova/ancova/manova?

Do there exist welch's repeated measures anova,ancova for unequal variances or does one have to run a mixed-effects regression or friedman test? Is it possible to generalize this methodology to ...
2 votes
2 answers
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What do double superscripts mean in an ANOVA table of 'ad hoc' results

What is this alphabet (a,b,c) and what does its combination mean in the table? I have read a lot of literature similar to my work and it shows that most of the researchers have used different ...
-1 votes
1 answer
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Non-normal distribution in anova - a big problem or not

Please don't close my question, it really is not a duplicate, no other answer on this forum is relevant to my case. Also, I have been advised that if I submit the spss output of my non-normally ...
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0 answers
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Control differences with dunnett adjustment chart [closed]

Why the answer is A? but store A is not appear in the chart
2 votes
1 answer
65 views

Statistical test to a large dataset

I have a big dataset with different kinds of human interventions in natural freshwater environments (categorical variable, one column) and the responses as control/ with intervention. It is a reunion ...
5 votes
1 answer
11k views

Nonparametric equivalent to mixed and 2-ways repeated measures ANOVA

I have run two psychological experiments. The dependent variable is a rating provided by the participant, that is, an integer number from 0 to 100. The first experiment is a mixed 2x2 design, with ...
1 vote
1 answer
47 views

How to calculate the R-square with the following figure?

The answer is 33033/80265= 0.4115?
8 votes
1 answer
985 views

Does Greenhouse-Geisser correction influence the effect size estimation, the statistical significance treshold, or both of them?

I discussed recently with one of my colleagues about the Greenhouse-Geisser correction for non-sphericity. I told him first that this correction is very conservative and that it would be more ...
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1 answer
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What does it mean when in a mixed design the "within" subjects is significant only when the "between*within" interaction is excluded from the model?

I have a mixed-design, 1 between (group A and group B) and one within (pre and post). Anova, as well as mixed-effects model, showed non-significant results in the between, in the within, nor in their ...
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What does it mean to do an ANOVA test between more than two groups?

How can you do ANOVA between more than two groups? What would the results of that even mean? As far as I understand it, ANOVA between A and B can tell you if the difference between A and B is ...
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Can I apply ANOVA across dilution factors?

I have 5 flasks. Flask 1 has only water (50 ml). Flask 2 has salt water (50 ml) at a certain concentration (say 10%). I call it dilution factor 1x. For flask 3, I create a 2x dilution solution by ...
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sum of classic eta squared greater than 1

I know that in an ANOVA with multiple factors (let's say x1 and x2), the sum of their respective classic eta squared (not 'partial' eta squared) cannot be greater than one and should approximate the ...
1 vote
1 answer
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How to compare the sensitivity of many countries?

My thesis question is asking whether biodiversity sensitivity differs geographically. I will assess all 5 pressures individually, but take 1 (pollution) as an example. My data contains time series for ...
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1 answer
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Is the deviance statistic in an Analysis of Deviance table a chi squared statistic

...
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Is it justifiable or acceptable to only check for moderation only in the experimental groups not in the control group

controlled experiment we have 5 groups: 2 Control Groups (CG, passive and active) 3 Experimental Groups (EG, Doseage of the Intervention). We also have two measurement time points T1 and T2 and ...
1 vote
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State-of-the-art nonparametric $k$-way ANOVA allowing heteroscedasticity

QUESTION: Can you recommend a nonparametric version of a multiway ANOVA that is also robust in the absence of homogeneity of variances? So, this is what I am looking for: (1) Nonparametric ANOVA (no ...
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1 answer
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GPower: Difference in Sample Size for ANCOVA vs. Repeated Measures ANOVA in clinical trials

I want to conduct a randomized pre-post intervention study with two measurement points (1. Baseline 2. Post-intervention) and two groups (Treatment vs. Control) and am currently trying to work out the ...
0 votes
1 answer
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What is the difference between the residual, lack of fit and pure error In F test for Regression Analysis?

What is the difference between the residual, lack of fit and pure error and how to calculate each of them in ANOVA F test for nonlinear regression?
1 vote
1 answer
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Noncentrality parameter Repeated-Measures ANOVA - formula vs. G*Power

I am trying to figure out the correct expression for the noncentrality parameter $\lambda_{ws}$ for the within-subjects effect in a one-way Repeated-Measures ANOVA with $k$ trials/groups. Comparing ...
0 votes
1 answer
431 views

Should I use ANOVA or MANOVA?

I would like to compare the performance of two algorithms A and B under various conditions. Performance is measured on a ratio scale. In a simplified setting, the input data set is a factor (DS1, DS2, ...
1 vote
1 answer
198 views

Pre and Post Survey Analysis in ANOVA Excel

I have a small end size of 6 participants. They all took the pre and post survey that had 10 questions with ranges associated with them. I did not ID the participants. I am wondering how to plug this ...
1 vote
1 answer
486 views

contr.Sum and standard error in R

I want to fit a linear model in R with a categorical variable that takes 3 possible levels. My goal is to check the effect of each level against a global mean, therefore I use contr.sum as contrasts. ...
1 vote
2 answers
56 views

ANCOVA vs linear mixed model in R, using different functions gives me different results

I have tried different packages, functions, libraries etc in R and my results differ, whether it be p values or F values or DF etc. This is especially true for my within variable (hemi).. between: ...
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Question on $2^2$ factorial experiment( replicates)

I am looking at a question, and it seems that the questions is making some assumptions and that they are providing extra information that is not necessary. Here is the question: Consider a $2\times 2$...
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How to find a decomposition of multivariate X along which y varies the most?

I'm looking for an existing algorithm which carries out the task shown in the title. My use-case in other words: I have a set of continuous independent variables (X) and a continuous dependent ...
1 vote
0 answers
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Interpretation of default Type III Sums in Squares in R

Many posts (i.e. here and here) discuss how the Type III sums of squares produced by car::Anova() in R are incorrect or nonsensical under R's default model parameterization, "contr.treatment"...
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1 answer
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4 way mixed ANOVA--Need help interpreting a 3 way interaction!

I hope I can clearly articulate my stats troubles! I am having difficulty interpreting findings related to a significant three-way interaction. My study includes one between-subject variable (Group 1 ...
1 vote
2 answers
64 views

Residuals of a 2x2 between-subjects factorial ANOVA are not normally distributed

Dependent variable: Emotional impact – measured by two ordinal variables (questions) on a Likert scale [1 (Least) to 10 (Most)] A composite mean score of the two variables was created named ...
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1 answer
238 views

What stat test to use, ANOVA, correlation? Comparing control with experimental group

I am really hoping someone can help me. I have my data all collected however I am really struggling how to analyse it. My supervisor is away and so I am kind of left here panicking over how to ...
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unbalanced type II SS ANOVA the correct test?

Good day, I have been pondering over this question for a couple of days now and maybe got lost in the details. I am a Psych Grad student, so my stats knowledge is not as deep as I would wish for. I ...
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1 answer
493 views

How to compare two time-series datasets?

I am trying to compare the financial performance of green bonds and conventional bonds by looking at their historical bond yields, bond prices etc. individually over a certain period of one year. I ...
0 votes
1 answer
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Difference between Within-Subject Contrasts and Pairwise Comparisons in a Repeated Measures ANOVA

I'm running a two way repeated measures ANOVA, and I'm having trouble finding what is the appropriate output to report (Contrasts vs Pairwise Comparisons). I have a 2x5 design. Lets say I have ...
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Unsure whether normality is mildy or severely violated, can I still use repeated measures ANOVA?

I am trying to run a repeated measures ANOVA in Stata on a dataset with 149 participants that each gave answers to 4 valuation questions (496 observations in total). I need to measure whether there is ...
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2 answers
31 views

comparing paired data between two groups

I collected 30 cases of paired data which includes serum creatinine before&after taking specific medication. And the cases are divided into two groups A and B each of which has different medical ...
1 vote
1 answer
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How to perform MANOVA with categorical independent variables

I have a dataset where the independent variable is sieve size (categorically either 25, 63, 100 or 150), and the dependent variables are length and width. ...
2 votes
2 answers
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How to find the significance of different levels of an interaction in a generalised linear mixed model?

I am using a glmm to find the effect of lockdown (Yes or No), sex (Male or Female), age (Young, Teenager, Adult) and site (A or B) on hormone concentrations (Continuous). Using lrtest, I have compared ...
1 vote
1 answer
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Running robust statistics: trimmed means or bootstrapping?

I am currently running some mixed ANOVAs for a 2x2 design (two groups, with pre- and post- test). Some of my variable are fine, but some of them violate assumptions for parametric testing, e.g. non-...
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paired Wilcoxon rank test but with 3 groups

What is the statistical test I should use if I want to run a paired sample Wilcoxon’s signed rank test but I have three groups to compare instead of two?
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Statistical Significance Testing and PCA Clustering, can I do both?

Is it appropriate to do nonparametric and parametric significance testing on clustered data? More precisely, I performed clustering on PCA dimension reduced data, and created cluster labels for data ...

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