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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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What to do when Breusch-Pagan shows heteroscedasticity but plot looks it might not?

So I'm trying to run a Least-Squares Means with a covariate. However when I run Breusch-Pagan test it shows heteroscedasticity even after either tukey or log2 transformation, however the plots seem ...
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which experimental design better fits?

I test the effect of a plant dose on the abundance of a specific microbe, cultured in glass tube in vitro. The treatment consist of 5 doses (0, 1, 2, 3, 4). Each culture tube receives one of the dose ...
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error residual identical for within subject ANOVA and between subject ANOVA with double the sample size

I noticed something interesting while playing around with data. If I conduct a 2-by-2 within subject ANOVA with 20 subjects my sum of square residuals look like this: ...
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nested random effects in mixed effect models across different levels, and associated DF

I would like to fit a mixed effect model to the following dataset, but I am having difficulties figuring out the best way to define the random effects. For each subjects (...
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Interpreting ANOVA results in the educational context

I have run an experiment in a six-week course to measure the effect of my educational treatment on student engagement. The treatment happens on weeks 4 and 6 of the course (for all of the students) ...
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Non replicated vs replicated field trial

I need to conduct a pesticide efficacy trial on avocados. I have been asked to describe two different trial approaches: replicated and non replicated. I have drawn the two trial design options. ...
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F ratio independence of numerator and denominator

For a particular hypothesis testing problem I have the quantity $F = \frac{\sum_{j=1}^{k} (\overline{X_j})^2}{\sum_{j=1}^{k} \sum_{i=1}^{n} (X_{ji} - \overline{X_j})^2}$ where $X_{ji}$ is the $i^{th}$ ...
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Can growth Curves be tested for signifcance variance between replicates uisng an ANOVA

I have a dataset that tracks barnacle size (shell length - dependant variable) growing on 3 independant buoys (that are identical). The measurements are taken every 1 week interval (independant ...
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What does the sum to zero constraint mean?

In an ANOVA model, there is a constraint that the coefficients must sum to zero. What does this actually mean? I do understand the reason why you might want to make them sum to zero, i.e. to have two ...
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What is point of transformation if the effects does not change?

with a question related to transformation. I have done a linear mixed model using the formula ...
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ANOVA or T-TESTS on Z-SCORED data

Let's assume that we have results from X people for 3 different variables. The scores are not on the same scale (for example they're not scores on the test when you can simply reach from 0-10 points). ...
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Q. Differences between 2 groups, randomly assigned to either a Control or Experimental group, testing the same variables [closed]

2 fluency groups (String): Monolinguals (Nominal) or Bilinguals (Nominal) in both groups each participant is randomly assigned to either an (String): Explicit control group (Nominal) or an Implicit ...
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Post hoc for Levene test

I have a problem regarding my data analysis. One of my hypothesis is basically that my groups will differ in terms of spread of the scores, indicating that there would be a difference in extremity ...
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ANOVA is significant but coefficients aren't

My master thesis investigates the relation between stock raw returns and sentiment scores. To make a conclusion there is a multiple linear regression with the mean sentiment, the variance of the ...
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Why does “ smooth term” have “parametric” effect?

I read a blog about Generalized Additive Model (GAM). In this blog, the author used summary(gam1), then some information is printed: ...
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Is one-way repeated ANOVA suitable for data

I have a question regarding the use of a one-way repeated ANOVA or mixed model for the data I am using (in STATA): The data was drawn based on negotiations between two people in a quiz show. The ...
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How to make sure if the residuals are normally distributed? [duplicate]

Hello, I have a fairly big dataset containing 11000 data points. I am doing a ANOVA for my traits. But before that I have to make sure if the residuals are normally distributed or not. So, I did a ...
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Accuracy of evaluation from ANOVA and T-test result?

My limited understanding tells me that ANOVA and T-test can be used to show significance or correlation by using inter-class and within-class variance. In a research paper, participants were asked to ...
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Two way ANOVA with percent change

I have two groups of animals: "active cycle" and "inactive cycle". Within each group, there are two groups: "control" and "treated". I measured the levels of a specific receptor for each animal in ...
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Do ANOVA & MANOVA require balanced levels?

I have one independent variable with two levels, or categories, and four dependent variables. When doing a MANOVA or ANOVA test, how important is it for the number of observations in each category to ...
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A two mixed ANOVA showed no significant interaction, but showed a statistically significant main effect of time, Do I need to run a paired T-test?

I did a mixed ANOVA with one within subjects factor with two levels 'time' and one between subjects factor (control + intervention). Its a comparison between INT or CON on scores pretraining and ...
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Split split plot: defining expected Mean Square error term for calculation of F values

Note: my endgoal concerns multivariate analysis but I do not believe my question is specific to this setting Motivation: the RRPP R package allows to analyze composition data (i.e. multivariate) ...
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Mixed ANOVA question

I have a 2x4 mixed ANOVA design for my experiment which has one between-subject factor (group-type) with 2 levels (native and non-native) and one within-subject factor (no. of repetition) with 4 ...
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confused about effects vs. means parameterization in R - which is right for Anova?

I'm running a few GLMs and using the effects (e.g. glm(var1~var2...) ) and then means parameterization (i.e. glm(var1~-1+var2...) -- the one without the intercept). I understand that effects gives you ...
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Two-factor ANOVA: What should be done when each cell has only one observation?

I have a data set, described as the measurement of insecticide found through four different extraction methods, A, B, C, and D. A measurement for each extraction method is made under the conditions ...
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Help in Two-way ANOVA with Significant Interaction

(note: I removed the original table because there were some mistakes in it. I preferred to use R annotation of Sal's answer.) Hi everybody, I got the following results for an experiment of ...
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Split Plot Analysis Interpretation

This is the R output I was given for a split plot analysis. I think I'm on the right track with my interpretation, but I want to make sure. Q1: What should you look at first? If the treatment*year ...
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How to properly represent a sum of interactions in ANOVA?

I would like to include an ANOVA-style linear model in my work that shows the main effects but has interactions lumped together in one term for brevity. When I do the analysis I will include the ...
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How safe is that to ignore homogeneity of variances test and continue with Post hoc test?

I want to know if average time people spending on their favourite social media are statistically different. I consider here five groups, and the total number of participant is 700 persons. I have ...
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NLS model comparisons by ANOVA

I am comparing NLS models from two groups, males and females. I compared the models by ANOVAs, but I am hesitating which is the correct model comparison to use: a) Subgroup Males vs Subgroup Females ...
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Chi Square embedded in an ANOVA model?

I have treatment->outcomes count data, which is obviously modeled by a chi squared, but there are several separate ones, let's say 3. I could run 3 separate chi squares, but I want to ask what would ...
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How to compare or evaluate different ratings

First of all, I would like to state that English is not my first language so apologize me if I use the wrong terminologies. In our company we collect reviews for our branches, so after each client's ...
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How to test seasonality of time series using One way ANOVA test?

I did perform a one way ANOVA test on my data, I'm having problems understand the results, my p-value is 0.0721 .
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Dumb question about splitting groups for statistical comparisons

I have a dumb question that I cannot answer based in my biological background. I conducted one experiment with 5 replicates and 4 treatments. There were two goals: the first goal was to elucidate ...
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Test difference of means between subgroups

I have a collection of N samples from which I have computed all pairwise Euclidean distances. The samples can be divided in 3 distinct subgroups. I want to test if the average distance of groups is ...
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Nested or Crossed ANOVA?

I am uncertain of the model that needs to be used in this case (nested vs. crossed), so first I will present the problem and then I will ask my questions. I am interested in knowing if the total ...
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Which multivariate test on repeated k-fold cross-validation with collinearity?

I am running repeated k-fold cross validation (5x5-fold) for comparing two models based on 3 dependent numerical variables (X, Y, Z) and 4 independent categorical variables (A (two groups), B (five ...
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4 x 4 x 4 Factorial Design or 4 x 4 Factorial with Blocking?

Problem here: https://imgur.com/Nl8AWie I was thinking that this problem might just be a 3-factor factorial design, since obviously the ad campaign and packaging are factors (we're interested in ...
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Comparison Tropical Storm Wind Speed

I am investigating wind speed of tropical storms between 2 years. There are an unequal number of storms per year, however want to test if the wind speeds are significantly similar or different. I ...
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Violation of univariate normality of residuals for DV in MANOVA. Can i trust non-significant results?

My design is one IV (control vs patient) measured on 3 different composite structures, consisting of 8, 3 and 2 DV from a behavioral test. The measures are t-scores based on norm groups for the test. ...
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Accuracy vs Precision: Can I use the Sphercity Assumption data in a meaningful way?

I understand that when conducting a repeated measures design with say one factor having three levels (Training: None, Standard, New Method), in the analysis you want the sphercity assumption to not be ...
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Can one use parametric tests (e.g. ANOVA) if part of the data/ variables meet normality criteria but others not?

I want to compare differences between two groups(n1=26, n2=18) regarding their performance on different tests but also explore how each group performed on different times of these tests. I am ...
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How to deal with different scales of significiance with a lmer model?

I did a linear mixed model and found only one significantly correlated variable. If I do a simple linear model other variables seemed to be correlate. How is it possible ? Is it because of different ...
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can you report non significant results from a 2-way ANOVA with unequal variances?

i have 2 independent variables variable a - 5 levels - unequal variances variable b - 3 levels - equal variances with 4 replicates each treatment I have performed 2 separate Welch's test for each as ...
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Two way repeated measures ANOVA with varying repetition

I measure the response to two different stimuli. For one stimulus measurements were taken three times and the other stimulus they were taken twice. Is it possible to do two way repeated measures ANOVA?...
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TukeyHSD p-value is less than t-test p-value

I have some data where when I do t.test for a specific pair of groups, the p-value is (barely) higher than when I do TukeyHSD ...
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Dissertation- how to conduct post hoc on a four-way ANOVA

I am currently in the end stage of writing up my dissertation. I have conducted 4 four way ANOVA's (between groups)- example below 1) the effect of assessment preference (2 levels), somatic group (2 ...
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What Null hypothesis does vegan::anova.cca(by = “terms”) test against?

I ran a distance-based Redundancy Analysis with the vegan R-package. Statistical significance of axes and explanatory variables can be tested with the anova.cca() function. Form Legendre et al. ...
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Should I use repeated measures anova? and what post hoc should I use?

I have an independent variable which is observed 3 times over the span of 78 hours (24, 48, 72) respectively. Should I use repeated measure anova or should I treat the hours of observation as a ...