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 to visually check for homoscedasticity? [duplicate]
I want to know what to look for in a boxplot, when we want to check for homogeneity of variances among groups, which is an assumption in ANOVA.
I used this codes to get a boxplot:
'''boxplot(log(...
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Anova model assumptions. How to go by?
I have a data frame that contains a continuous response variable measured on different species, at different elevation and month of sampling as explanatory variables. I want to analyze how the ...
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Data is not normal, want to test for interaction too Any non-parametric test? [duplicate]
I have a sample size of $310$ individuals that comprises samples collected along the elevation gradient and at different times. I want to see how the variables differ along the elevation, and with ...
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Can Tukey HSD groups be of slightly different sizes?
In my Tukey HSD I have some groups with 5 data points, and some groups with 6 data points. Is this allowed with Tukey HSD? The only option would be to remove 1 data point from some groups, and that is ...
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Tukey HSD - can I add an additional data point to each group?
When computing Tukey HSD I have multiple groups. For a homework assignment, I realized I accidentally included an additional data point in each group, which is the average of the group. Is this ...
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Error when trying to perform repeated measures ANOVA in R [migrated]
Consider this data frame:
...
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Different results between ANOVA and Linear Mixed Effects
A set of subjects from two groups are requested to perform a test after a sleep session of type A and then after a sleep session of type ...
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Contrast between linear mixed-effects model and two-way ANOVA
Let $Y$ a real positive variable. I have a data frame with the measurements $X = mean(Y)$ of four distinct categories of subjects:
Healthy control during control condition
Healthy control during ...
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G*Power sample size calculation for ANOVA
I'm trying to do an a priori power calculation with G*Power 3.1.9.2, but I don't know which test to choose and what to enter in "number of groups" and "number of measurements" for ...
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Confusion about replication in ANOVA [closed]
Set Up
It's about finding out which formulation (concentration in percentage) and soaking time of formulation yields to a better measured outcome.
In the table below, Minutes represent soaking time ...
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Performing ANOVA with missing data
I conducted a two-factor experiment with 3 replications on flower diameter under nutrient treatments. I got the data that look like this:
Factor A
Factor B
Replication
Flower diameter (cm)
A1
B1
1
2....
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Testing change in ratios
I do not know how to perform this statistical test. I have a proportion of a bodily liquid substance, and I am interested in the ratio with respect to another. For instance, ratio of water (20l) and ...
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Non-significant results when running Kruskal-Wallis, significant results when running Dwass-Steel-Critchlow-Flinger pairwise comparisons
I am writing my Master's thesis on adult's performance on cognitive and linguistic measures. I have four age groups and am investigating if there is an age difference in the performance on summarized ...
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Degree of Freedom in DoE modeling
Past the standard full factorial and fractional designs, I am getting the impression that non-regular designs (OME, Hall, mixed-level OA, etc.) are just trying to fit in as many factors as possible. ...
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What is the best statistical test for percentage of respondents data?
My data consists of three columns
A is the percentage of those who answered 'Yes' on question 1
B is the percentage of those who answered 'Yes' on question 2
C is a number that represents a score. ...
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Post-hoc test for Bayesian ANOVA in R
I set up an ANOVA to test for a 2-way interaction. However, for my hypothesis I would need to test whether the levels A and B of facor 1 are different for each level of factor 2. In a frequentist ...
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T test or a different analysis? advice
I want to make sure i get the right analysis.
I have taken chemical measurements of soil at two grasslands at two depths. For example soil PH.
So one with chemical treatment and one without at two ...
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Statistical model for multi-subject multi-trial group comparisons
I am quite a novice in statistics and I have a complex model (at least for me) that I need to build for a test. I have a treatment plan and I am doing some frequency measurements in different regions ...
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How to consider independent samples in a mixed-design experiment?
I collected data from an experiment with a mixed-design, specifically a 2x3x4 mixed-design, where the factors are populations (2 levels), conditions for the first population (3 levels), and conditions ...
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Regression coefficient before vs. after demeaning X
It is well known that $\beta = (X^{T}X)^{-1}X^{T}Y$ for linear regression. While experimenting with this, I found that $\beta$ (excluding the intercept term) remained the same before and after ...
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Statistical analysis to interpret beta effect size for two different elastic net model
I have two elastic net model and I want to compare their coefficient to say if they have any significant beta effect changes across these two models.
I thought of using Anova but realized since we don'...
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When detecting outliers for an ANVOA test for multiple groups, should I do this for the whole population sample or by group?
I have data that is grouped by 5 groups. I want to check for outliers as part of a one-way anova. Should the check for outliers on the whole sample, or by group? I am using box plots to look for ...
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Assessing the impact of one variable on multiple others
I have a dataset of patients with multiple parameters recorded, such as glucose, diabetes, O2 concentration, etc. I want to check whether glucose levels are in any way associated with other parameters....
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Comparing statistical difference between two trendlines/slopes
I was involved in bench testing for a medical device from 2 companies. How much one end of the device can rotate (0 to 180 deg) translates to rotation at the opposite end (0 to 180 deg) was measured. ...
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Use of simple statistics for matched study designs
This might be a silly question, but I have always found this confusing. In a case-control study one selects participants to the study based on having or not having the outcome, in addition to some set ...
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Non-constant treatment periods for A/B test samples
I have 4 A/B testing samples with 4 treatment groups and their 4 respective control groups (n=10000~), with known (but not distinct) treatment periods. The issue is that the treatment periods overlap ...
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Sample size calculation for RM ANOVA; the difference between WebPower package in R and G*Power 3.1.9.7
I've run two sample size calculations with the WebPower package in R and G*Power simultaneously.
The conditions I've done are;
Case 1
Cohen's f = 0.2756987
Number of groups = 1
Number of repeated ...
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Partial eta square values summing to greater than 1
I am trying to run a factorial ANOVA analysis with partial effects, but it seems that my partial eta square values are totalling above 1, particularly when I specify my contrast with Type II or Type ...
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Unsure of statistics needed while working with replicates
I apologize if the question is considered too broad, but I'm hoping to get at least a basic starting point as I'm somewhat stuck with how to approach this.
I am working with community ecological data-...
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What am I doing wrong with my one way anova in R? [closed]
I am trying to run a one way anova on some data listed below. But when I run the code, it does not give me a p value. I'm not really sure why this is happening.
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Kenzo Cotton
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non-central F-statistic confidence intervals seem inconsistent with ANOVA p-values
I have done a series of one-way ANOVA tests. For each test I have calculated the corresponding alternative hypothesis F-statistic and confidence intervals, based on the degrees of freedom involved and ...
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How to compare nested models in glmer ()
I am testing random intercept models using the glmer() function in R.
I learned from my stat class I need to use FIML, not REML to compare nested models.
However, <...
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Comparison of parameters for enzyme kinetics using bootstrapping and ANCOVA. Is this right?
I'm analysing the breakdown of substrates (i) that were previously treated with a first enzyme for defined time periods (j), and then subjected to a second type of enzyme (l) that will generate the ...
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How to conduct post hoc paired comparisons for mixed effects model?
I am working with some biological data where I am trying to compare 5 categories of genes by expression which occur at different loci (locations on the chromosomes). I have samples from different ...
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ANOVA type III strange results
I am performing some simulations for a power analysis but, I am finding some strange results.
In a scenario of a two-way ANOVA (5*5) where I check a relevant interaction (One level of Factor B ...
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Measuring the effect of treatment on variable over time
I am trying to establish whether a treatment had a significant effect on a variable over time. I have raspberry plants treated with $5$ concentrations of compost ($0$%, $5$%, $10$%, $15$% and $20$%) ...
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Which type of ANOVA should I select for a Power Analysis of a Factorial Design
I am trying to develop a function to simulate datasets, in order to perform power analysis on a Factorial Design (for example 3x5 design). In my case, I'll be interested in testing both differences in ...
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Transformations to meet heteroscedasticity
I have a dataset containing angles. They represent the bending angle that a seedling makes to go toward light. I have two factors: treatment and genotype, so I use a two way ANOVA. However, the ...
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SE and SD in a mixed ANOVA design
I have conducted a mixed-design ANOVA with a between-subjects factor (Group: Control Group [0] vs. Intervention Group [1]) and a within-subjects factor (Time: Baseline [0], Follow-up 1 [1], and Follow-...
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SIgnificant ANOVA but not significant post hoc ... what can I do?
I am analyzing some IHC data on the density of cells in two brain regions(factor 1) in two closely related species(factor 2). My data is composed of an n of 6 for each species and is not normally ...
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Different results in 2 way ANOVA with interaction depending on the order of the factors [duplicate]
I'm trying to do a two way ANOVA on a dataset with 2 fixed effects factors (Genotype and Treatment). However, depending on the order of which the factors are in the model formula, I'm getting ...
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Null hypothesis for ANOVA for regression
Context: I know the "classic" ANOVA framework: we have $n$ groups and $k$ measurements of a variable $X$ for each group. Let $µ_1$, $µ_2$, ..., $µ_n$ be the mean of $X$ in each group.
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Robust ANOVA t2way unequal sample sizes?
I have some parameters that I would like to analyze with a two-way ANOVA. The treatment groups have unequal sample sizes (n=9, n=36, n=36, n=36) and the data do not fulfill the requirement of normal ...
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Repeated measures ANOVA for pre-post and post-post comparison + multiple comparisons problem
In my experiment, subjects had to answer a number of unrelated questions before and after an intervention. We had two different interventions, and all participants underwent both interventions in ...
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Analysis of ANOVA Table to Determine Polynomial Degree
Using time-series data, I'm trying to determine the optimal polynomial degree to use for my regression. To do this, I chose to run an ANOVA test on 5 models, the first model's degree is equal to 1 and ...
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Impact analysis of individual independent components
I need help in understanding how we can analyse the impact of an individual independent variable (campaign media type in this case) on a dependent variable (sales performance here) when not using the ...
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Appropriate statistical test evaluating difference in proportions between two groups over multiple time points
Over the course of a year, I took samples from dogs and their beds and looked for the type of bacteria in the bed and in the dog every month. I did not get samples from the same dogs or the same beds ...
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Quantitative Proteomic Analysis : ANOVA or MANOVA?
So, this may be a really dumb question but I'd rather ask it now than 3 weeks later when I'm neck deep into problems. The title is kind of self-explanatory but I'll expand a bit :
I've been tasked of ...
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ANCOVA in within-subject design
I have two questions regarding an ANCOVA analysis in SPSS in a within-subject (i.e., repeated measures) design (e.g., an experiment with 3 measurement timepoints):
when checking ANCOVA assumptions, ...
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