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Questions tagged [levenes-test]

Statistical test used to assess whether the variance differs across a number of groups. This test is sometimes used to justify the assumption of homogeneity of variance when using ANOVA or $t$-tests.

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Modeling interaction in variance

I run an experiment on both men and women participants, where I manipulate an independent variable. I know that the manipulation causes greater variance in the outcomes of the experimental group (a ...
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Ancova for unequal variances [duplicate]

What is the best way to compare two non-homogeinous populations (Levene's) with covariates (e.g. age). I know ancova assumes homogeneity. Is there a way around this? Many thanks
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How to deal with unequal variances in repeated measures ANOVA

Angry Birds is a video game in which you fire birds at pigs. A (fabricated) study was set up in which people played Angry Birds and a control game (Tetris) over a two-year period (one year per game). ...
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Appropriate method to assess scatter or variation in groups with dramatically different means

I am working on a product fabrication process, and I want to demonstrate the consistency of my product. To do this, I am trying to measure the variation in the extent to which a biological material is ...
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Use of supportive inferential statistics (e.g. Levene's and normality tests) in underpowered samples

We know that underpowered statistics greatly increase the probability of a type II error (by definition), meaning a greater chance of failing to reject the null hypothesis despite the existence of a '...
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Three Factor Multiple Comparison Post-Hoc Test for Levene's Test

My research question is to find out whether or not my samples are exhibiting any significant differences in their variance in response to three possible treatments. Here are my possible groups: ...
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Ruling out collusion in peer evaluation

In my class I have groups of students making presentations and the rest of the class evaluates them. Since their scores are curved the students do have an incentive to collude and mark other teams ...
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Comparison of variance between two samples with unequal sample size

The primary goal of my analysis is to compare the variability in the response variable, Blood Pressure, between sample1 and sample2. The secondary goal is to test for a difference in means. I do not ...
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I can perform an F-Test if Bartlett and Levene fail, but Shapiro-Wilk Pass?

I'm going through the assumptions on an F-test and I want to make sure I've gone through each item so that my results are valid. Data is normally distributed; The samples are independent from one ...
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Non-parametric alternative to simple t-test

I have five numeric variables of two populations (each of them with 60 individuals) and for each of those five variables I want to know if there is difference in the means. I was trying to use a ...
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Interpreting new Levene Statistic shown by SPSS

I want to perform a between-subjects one way ANOVA on my Data. I have 4 experimental groups. I performed the tests of normality and homogeneity of variances. The output from SPSS for homogeneity of ...
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Performing a two-way ANOVA, I get a non significant Levene's and a significant interaction effect. What it the next step?

In the case described above, our Professor instructs as to interpret the simple effects by using MSwithin of the two-way ANOVA. In case the Levene's test is significant though, he instructs us to ...
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Levene's test significant in 2x3 mixed design ANOVA

I'm trying to run a 2x3 mixed design ANOVA. Participants were measured on three different domains at two different times. One out of the 6 sets of results violates Levene's test while the rest do not. ...
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Statistical tests, when data are not normally distributed & variance is not equal

I have a data with two variables - one variable is quantitative, and one is nominal (4 categories). I ran the normality tests and it turned out that this quantitative variable is not normally ...
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Levene's test assumptions

Does the Levene's test have any assumptions? If so, what are they? To my surprise, neither my textbooks or Wikipedia, mention any assumptions for this test. But I seriously doubt that the test doesn'...
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Smallest possible sample size per group in Levene's test

Recently learned that Levene's test is a one-way equal-variance ANOVA done on absolute values of residuals calculated from the mean within each group. For one-way ANOVA the minimal sample size seems ...
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Levene test in R

I tested for equality of variance between two groups in R ...
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Testing equality of variances in panel data

I am familiar with Levene's test (Wikipedia link) for equality of variances, which is robust to non-normality, but assumes observations are independent. Today I was wondering what to do when you want ...
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One-sided test of equal variances with small (but equal) sample size and non-normal data

I have two groups, each with 6 observations. One group was generated by an old test method. The other group was generated by a new test method. I would like to test if the new method produces more ...
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Test for homogenity of variances, Levene's test and fligner-kileen yield different results

I have two sets of data, in which the first dataset contains 3346 values and the second dataset contains 1168 values. The variance of the first one is 13.88% and variance of the second one 13.96% The ...
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ANOVA one way: Levene test is significant. Welch and Brown Forsythe Test are the solution?

I trying to run a one-way ANOVA to compare 3 groups (Northern, Center and Southern regions) but Levene test is significant. Kurtosis and Skewness are ok but the equal variances assumption is violated. ...
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How to rectify Heteroskedasticity/Failed Levene Test in Linear Mixed Models?

I am newer to mixed models and ran into a confusing spot with one of my models because it violated the assumption of homogeneity of variance. I am running this in R and using lmer from lme4. Sample ...
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Normality of distribution: Shapiro-Wilk and Levene tests

I have Likert-scale data from an experiment with 5 conditions, each of which has a different treatment and one is a control group. The goal is to compare the effect of the treatment between the ...
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What affects Levene's-Test Sig. value?

I did a Standard Error Plot of my two treatments, and homogeneity of variance appeared to be justified (there was only a slight difference in variance). However, then I ran Levene's during my ...
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What type of test should I use on my data?

I am testing gas mileage between three brands of gasoline. I am testing on a small population of 10 cars. Hypothesis: Cars using higher grade gasoline will have a significant higher gas mileage than ...
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Is it acceptable to do an unpaired t-test without Levene's test for equality of variance?

I collected data for my study to compare with the published norms of two other studies. All three groups are from different populations (based on occupation). I will be using a two-sample independent ...
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Homogeneity of variance violation in a 2x2 mixed factorial ANOVA with normally distributed data

I'm wanting to conduct a 2 (phase: P1, P2) x 2 (group = G1, G2) mixed model ANOVA, whereby phase is the continuous within subjects variable and group is the between subjects variable. The phase ...
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357 views

Mixed-ANOVA Design - Assumption

1) In a Mixed-ANOVA design, with one-between subjects (2 levels) and one within-subjects test (2 levels), do we normally check the Levene's output to ensure that we are not violating the assumption of ...
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Levene's Test on 2-by-2 Mixed Factor Anova

It is my understanding is that a Levene's test is simply looking at to see whether there are any differences between the differences of the mean. Here is some data: ...
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Assumptions on the Levene's test

I'm trying to conduct the Levene's test for 10 non-normal samples to study an eventual heteroscedasticity. I was trying to justify my applying of this test, but I can't find it's clear assumptions. ...
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Advice regarding statistical analysis - two way ANOVA for a data set with unequal variances?

I have a data set classifiable by gender (male and female) and genetic status (WT and mutant). The WT data is mostly consistent with tight standard deviations, whereas the mutant data is highly ...
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2x2 ANOVA with non-normal distribution and Levene failure

I am doing an MSc dissertation in psychology at the moment. I have collected data from 307 groups, and I am trying to run a 2x2 ANOVA. The DV is 'number of conversations'. One IV has 2 levels (yes or ...
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717 views

Differences between Breusch-Pagan test and Levene's test

I am trying to check homoscedasticity of Residuals to use an ANOVA in R with data with one variable and three groups. I have been checking options to do it, and I would like to know when to use a ...
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Test for equality of relative variation

So when I have two vectors of unequal sizes with different means and different standard deviations. One has coefficient of variation of 10% and the other 15%. Which statistical test would I use to ...
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342 views

How to calculate statistical significance when a Levene significance value is not given?

I have performed an independent t-test on SPPS and retrieved these results: No Levene significance value was given and so how would I know whether my results are significant? Would I just divide the ...
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Most suitable test to check homogeneity of variances

I'd like to apply a t-student test to compare diferent samples to reference one using R but first I'm checking if my data meets the requirements for t-test so I removed outliers using the function rm....
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Test for monotonic trend in group means

I have dozens of groups of an observed variable. The number of observations in each group varies and the variance between groups is different. The mean of each group is the variable of interest. The ...
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Is Levene's test necessary?

My friend told me to use Levene's test to check the assumption of homoskedasticity before applying the two sample t-test. I think most people that use linear models don't do that. They check the ...
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One of my groups (out of 3) doesn't have normal distribution, while a One-way Anova showed unequal variances (using SPSS); what to do?

I have an experiment where I'm testing the effect of a drug on behavior, measured in seconds. My drug group doesn't have normal distribution, probably because of a bimodal pattern: 6 of the 8 are ...
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How can I test for differences in variation between groups in a mixed model (lme4)?

I would like to test for differences in variation, not in means, between two sites. By looking at a boxplot of my data I see that bird song in one site look much more variable in length than in ...
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Significant Result in Levene's Test

I am very confused right now. I ran Levene's test on my data and got a p-value of 0.000, meaning that variances are very heterogeneous. I transformed the data but no method can make them homogeneous. ...
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ANOVA and Kruskal-Wallis Test in One Study

I am currently analyzing the results of my study which deals with several dependent variables. I have tested the data for normality and homogeneity and all but one passed the assumptions for ANOVA. ...
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How to test difference in variability with paired data?

I am dealing with what seems to be a very simple problem, but my statistical knowledge is now a bit rusty, and I can't think of any good solution. I tried to cast my problem in a simpler one, hope it ...
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Mean separation equivalent for a test of equal variance

I am working on a project where consistency the most important factor. It involves a 4 input risk rating system. I am interested in what inputs are the most variable/sensitive to assessor bias. When ...
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358 views

Detect outliers (anomalies) in salary data

I have a dataset with over 10,000 employees and I'm interested in performing some tests to identify salary anomalies. For example, paychecks for some employees might look like this: ...
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Can a Levene's test be conducted with only summary statistics?

My research question specifically deals with testing the variances of 3+ groups for significant differences. I'm not looking to test an assumption of homoscedasticity for an ANOVA or any other test, ...
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911 views

General Linear Model Univariate with unequal variances - what are my options?

I'm using SPSS to run a GLM (general linear model) univariate with 1 fixed factor (Treatment) and one random factor (experimental replicate). There are 4 treatment groups. The measurement is number of ...
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Effect size for difference between variances / Levene's test

I have tested a hypothesis of equal variances (using Levene's test), and would like to report an effect size alongside the significance test. Unfortunately, I cannot seem to find any references to a ...
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Do I have a justified reason to exclude a non-significant covariate from my ANCOVA? How interesting is unequal variance?

I am comparing glutamate concentrations across groups (2 groups). I planned on controlling for age and IQ, simply because this is what is always done in cognitive neuroscience. When doing this, age ...
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Two way ANCOVA with slight heteroscedasticity

I am about to perform a 2-way ANCOVA but I reject the null hypothesis in Levene's Test with a p-value of 0.023. See standard deviation and sample sizes below. I googled up and down and found people ...