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Questions tagged [anova]

ANOVA is an acronym for "analysis of variance". It is a widely used statistical technique to analyze the source of variance within a data set.

Overview

Although ANOVA stands for ANalysis Of VAriance, it is about comparing means of data from different groups. It is part of the general linear model which also includes linear regression and ANCOVA. In matrix algebra form, all three are:

Y=XB+e

Where Y is a vector of values for the dependent variable (these must be numeric), X is a matrix of values for the independent variables and e is error.

Tag usage

  • SO questions on ANOVA should be about implementation and programming problems, not about the statistical or theoretical properties of the technique.

  • Consider whether your question might be better suited to CrossValidated, the StackExchange site for statistics, machine learning and data analysis.

In scientific software for statistical computing and graphics, function aov implements ANOVA. Note that function anova does something else. See When should I use aov() and when anova()?

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ANOVA LMER Eta squared

I used the lmer package to run mixed models, when I use the anova function to retrieve the anova results, everything works. However, when I try and calculate the eta squared, I consistently get the error below. Any ideas? Dyestuff is a dataset…
Lowpar
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Error in lm.fit(x, y, offset = offset, singular.ok = singular.ok, ...) : 0 (non-NA) cases in r with repeated mesures ANOVA

When I use anova_test() function(from rstatix package) to do two-way repeated measures ANOVA, an error occur: Error in lm.fit(x, y, offset = offset, singular.ok = singular.ok, ...) : 0 (non-NA) cases I check my data and there is no missing…
zhiwei li
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Unable to run Two-way repeated measures ANOVA; 0 (non-NA) cases

I am trying to follow the tutorial by Datanovia for Two-way repeated measures ANOVA. A quick overview of my dataset: I have measured the number of different bacterial species in 12 samplingsunits over time. I have 16 time points and 2 groups. I…
Maddie
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Python - Need help in solving "Load the R data set mtcars as a pandas dataframe." problem

I am working on this problem and unsure on how to proceed. Load the R data set mtcars as a pandas dataframe. Build a linear regression model by considering the log of independent variable wt, and log of dependent variable mpg. Fit the model with…
NARMADA SEKHAR
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selected output for Tukey's HSD in two-way ANOVA in R

I have a large data set with multiple variable. I need to do two-way-ANOVA and then post-hoc pair-wised multiple comparison using Tukey HSD. the head of my data for first 25 entry is like this: > head(my_data2, 25 ) CellType variable value 1…
Lionette
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One-way Anova loop through pandas dataframe - results in a single table

I have a pandas dataframe containing 16 columns, of which 14 represent variables where i perform a looped Anova test using statsmodels. My dataframe looks something like this (simplified): ID Cycle_duration Average_support_phase …
underclosed
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How to generate a compact letter display for pairwise TukeyHSD

I'm having trouble generating a compact letter display for my results. I've run an ANOVA followed by Tukey's HSD to generate the p values for each pair, but I do not know how (or if it is possible?) to assign letters to these p values to show which…
Amy
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Undefined columns selected when performing TukeyHSD

I am very new to R and coding in general, so I apologize in advance for anything that may seem silly. I performed an ANOVA and wanted to do a TukeyHSD on my data. At first, it worked fine. Then I created two data sets. In each one, I sorted my data…
Jennifer
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How to update code to create a function for calculating Welch's for polynomial trends?

I am trying to reproduce the SPSS output for significance a linear trend among means when equal variances are not assumed. I have gratefully used code from http://www-personal.umich.edu/~gonzo/coursenotes/file3.pdf to create a function for…
Cassandra
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for loop to conduct anova test in all dataframes in a list in r

I have my dataframe: df <- read.table(text = "id G1 G2 G3 value 1 A D20 TAN 1 2 A D20 TAN 9 3 A D20 TAN 10 4 A D40 TAN 8 5 A D40 TAN 3 6 A D40 TAN 9 7 A D60 TAN 5 8 A D60 TAN 5 9 A D60 TAN 10 10 B D20 TAN…
Lennon Lee
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Anova test in Python with a very large number of Groups

I have a relatively big dataset (approx 273,744 records) containing among others names of people and the dioptrics power they use: Name | Dioptric | Gender | Town | ----------------------------------- 'John' | 0.25 | M | A | 'Jack' | …
Artemis
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Create data.frame from ezANOVA output

I've just ran a mixed ANOVA using ezANOVA and I need to create a data frame with the output for extraction into an Rmd but I cannot find any information on how to do it. I've previously used aov() and broom::tidy(), however tidy() cannot format the…
Julia M
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ANOVA for three subsets on R

I am a real novice with R. I have a .csv data file. I have created 3 subsets of data, which represent three different groups responses to a questionnaire. p_groupFMI = subset(data, M_freq==1) #n= c_groupFMI = subset(data, M_freq==2)…
Joseph
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How to extract residuals and read coefficients from the function Anova()?

I use the function Anova() in package car to perform a test with type III. But I have no idea how to extract the residuals or how to get the information of parameter estimates. Is there some way to do these like residuals(model) and…
A. Caikov
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Uses of typ in anova_lm()

Sorry, I'm new to python and stats. And I was curious about the typ in the anova_lm() function. What does typ 1,2,3 mean and how do they differ? This is an example code of the typ=2 used. aov_table = sm.stats.anova_lm(results, typ=2) aov_table
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