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 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.
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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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Can I have an IV which does not have main effect on DV directly but might have an interaction effect with another IV on DV?
I am inducing envy (IV 1) to see the effect on focusing illusion/anchoring bias (DV).
Since I am going to induce envy by showing attractive others' pictures,then gender will play a role because ...
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Batch effect significance
I'm doing a project where i study bending angles in plants, with different genotypes and treatments. I have done the experiment 4 times, so i have 4 different batches. I'm trying to take into account ...
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Difference between Repeated measures ANOVA, ANCOVA and Linear mixed effects model
What is the best way to analyze these data:
Subjects are divided in two "Group" (Treatment A and B).
"Weight" is recorded before and 3 months after treatment.
Outcome variable: ...
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median imputation or case deletion for small samples
I have a dilemma. I have a data set of different proteins from 4 groups of animals characterized by two factors: age (3 or 12 months) and presence of a certain gene (KO or WT). For each combination of ...
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Complete case analysis, multiple imputation, or instrumental variable analysis?
I ran a small study where all participants attended a psychological intervention, and completed measures at pre, post, and follow-up. Approx. 40 participants took part, of which approx. 5 did not ...
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Can you explain the logic behind degrees of freedom for interaction effect in multi-factorial ANOVA?
I am currently trying to build intuition for two-factor ANOVA by doing some simulation in Python, and some things are hard for me to parse.
I have an ANOVA with 4 levels of one factor and 3 levels of ...
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What is the variance decomposition method?
For $i = 1, \ldots, m$ and $j = 1, \ldots , n$ we have observations $x_{ij}$. We can assume that
$$
x_{ij} = y_{i} + z_{ij}, \qquad y_{i} \sim \mathcal{N}(\mu_{y},\sigma_{y}^{2}), \quad z_{ij} \sim \...
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Power Analysis for 8x8 factorial within-subjects design (required number of participants/samples)
for an experiment, I was asked to provide a minimum required number of participants using an a-priori power analysis. Thing is, I'm now really confused on how this is possible or even if it makes ...
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T-test vs. ANOVA [duplicate]
With two groups I can either perform ANOVA or T-test. Additionally I can have one-sided test, if I want to make sure I get the same conclusion from both tests and for t-test I choose alpha=0.05, I ...
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Repeated measures Ancova in R
I am trying to analyse my data but I am unsure if repeated measures ancova is the way to go.
I have a variable named "A" measured in three different conditions "1", "2" ...
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Repeated Measures Ancova In R
I apologize if I am not being very clear, I have basic knowledge in statistics! I am trying to analyse my data but I am unsure if repeated measures ancova is the way to go. I have a variable named &...
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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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Test for synergy using Bliss independance model for two drugs
I have a dataset of 40 patients which receive 4 different treatments, group 1, is placebo, group 2, drug A, group 3, drug B and group 4, drug A+B. Only one dose from each drug and combination. I would ...
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Statistical test for a biology experiment when plants were grown in 3 different solution concentrations
I have conducted an experiment for my Biology Internal Assessment in the IB Diploma Course where I grew Phaseolus coccineus beans for 14 days. This is the overview of my experiment:
Independent ...
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Question about Time 1/Time 2 analysis
I was hoping to get some input on the best way to test some data that I have collected (using SPSS).
In short, respondents make an evaluation at time 1, then complete a distractor task, and then ...
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What linear formula is this model fitting? [closed]
The rstatix R package has a wrapper around the aov called anova_test. It allows to pass ...
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GLM vs Kruskal-Wallis/ANOVA?
I am trying to analyse some data in R that has one continuous dependent variable (x) and two categorical variables (sex: M/F, surface: D/V). My main goal is to understand if sex and surface affect 'x'....
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Why anova disappear in robust regression [closed]
My question is this: When we run OLS regression, an ANOVA table is given but when we run robust regression, then the ANOVA table and adjusted $R^2$ values are not shown. Why?
I want to know the logic ...
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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, ...
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How to analyse binary responses for various factors, including interactions: chi square, mixed models, logistic regression, or ANOVA on percentages?
I run an experiment where subject had to recognize an emotion from various musical stimuli (which were composed with a certain emotional intent). There were 4 levels of emotional_intent, subjects ...
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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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Group comparison - aggregate data or compare means?
Let’s say I measure a parameter of interest out of a group of 10 genetically identical individuals (e.g., an inbred C57BL/6J mouse). I can compute a mean, SD or 95% CI from that sample. Then let’s say ...
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Error when trying to perform repeated measures ANOVA in R [migrated]
Consider this data frame:
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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.
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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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Unbalanced Two Way ANOVA
I am attempting to finish my stats on my Master's thesis and am having difficulties with which statistics test I should be using, and how to go about doing so. I have collected chl-a samples at 15 ...
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Why do we need to model lower-order effects in models with interactions?
I recently saw a paper with a four-way interaction. That already is difficult to interpret (maybe if you have 1 or more categorical variables but definitely near impossible to interpret if all ...
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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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2-way Anova on Unequal Group Proportions
I’m working on a dataset collected from a 2-way Anova design (kind of) on binary data. The purpose of the experiment is to explore how different types of email marketing incentives affect customers ...
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If using an adjusted F value (repeated measures ANOVA), should partial eta squared be adjusted?
I am using a procedure which, due to reducing error variance and resulting in artificially inflated F-values, requires the calculated F-value to be divided by (N-1)^2. The sources I have regarding ...
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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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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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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 ...
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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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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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Would you flag this data as fraudulent?
Let's suppose you have been given some data from a randomized block design with 4 repetitions and 23 treatments. After an initial inspection of the data, you notice that for 8 treatments all ...
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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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Synergistic effects: what statistics should I use?
I have one control group and three treatment groups. These three groups are treated with substance $A$, $B$, and $A + B$.
After treatment, the measurements compared to the control changed by $x,$ $y$, ...
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Is a Mixed ANOVA the same as a combination of between ANOVA + repeated ANOVA + between ANOVA?
In my study involving three conditions (control, treatment 1, treatment 2), I am interested in measuring 2 DVs at a pre- and post-exposure. So effectively a 3x2 design (participants randomly allocated)...
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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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