ANOVA stands for ANalysis Of VAriance, a statistical model and set of procedures for comparing the means of groups of related data. 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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ANOVA data prep - sum across

I have an experiment with two treatments (3 & 4 factors each) and 4 true replicates on 48 plots. Those experimental plots recruited various quantities of 25 different species so the dataset has ...
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21 views

Only binary predictors — ANOVA, regression, or other?

I am trying to fit a model to predict a quantitative response variable, using several binary variables. In particular, I am interested in measuring the relationship between one of the binary variables ...
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39 views

Should I perform multiple t-test or an ANOVA?

My causal comparative study seeks to three questions related to the hypothesis: a) is there a statistically significant difference between the academic achievement of 6th grade mathematics students ...
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17 views

Partition of sums of squares (ANOVA)

Can anyone explain the theory (or the formula) about computing Sum Sq (bold highligh below) related to regression items? The Wikipedia link gives an introduction on how to calculate the total, model, ...
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15 views

Tukey's HSD after Repeated Measures One-Way ANOVA

We compare the performance of >2 classifiers. Samples are drawn from n-fold cross-validations on the same data sets. We are aware of the fact that cross-validation makes the samples dependent, because ...
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28 views

How to obtain a complete ANOVA table from a mixed model in R?

I am using nlme in a mixed model: Y = a + b + a*b. fm1<-lme(Y ~ a*b, data = example.ento.mn, random=~1| Exp/Plant) a and b are fixed. random error: ...
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92 views

Hat matrix,$H=X(X^{\prime}X )^{-1}X^{\prime}$

What is the importance of hat matrix, $H=X(X^{\prime}X )^{-1}X^{\prime}$ in regression analysis? Is it only for easier calculation ?
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45 views

In R, what does anova(f1, f2, f3) compare?

I'm trying to understand the reason why anova(f1, f2, f3) and anova(f1, f2) gives me different result while anova(f1, f2, f3) and anova(f2, f3) gives me the same. Here's the code: ...
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1answer
56 views

Why do ANOVA p and F values change?

I am currently conducting a two-way ANOVA on a dataset and have noticed how significance and F values change dependent on the type of ANOVA I use in R. Why is this? For instance, if I run a two-way ...
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32 views

Can I do two factor repeated measures ANOVA with differing numbers of measures per group?

I want to compare reaction time in four groups but I have three measures (pretest,post test and delayed post test) only in one of the groups. it was impossible to give post test and delayed post test ...
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17 views

G*Power analysis -sample size calculation

My experiment is devised as follow: There are two different types of stimuli-- cellphones: android (android-1; android-2) and iOS (iOS-1 and iOS-2). A sample size of 60 subjects are divided into two ...
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22 views

How to do a power analysis for an unbalanced mixed effects ANOVA?

I need suggestions for how to calculate the $n$ required for 80% and 90% power for >30% change from baseline ($T_0$) at $T_1$ or $T_2$, drug vs. placebo, 2:1 ratio; 20% CV in test; factors: subject, ...
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23 views

sample frame representing the true population

(i) Is it true to say that if the sample frame is not a random selection (such as a convenience sample), then the sample frame is not representative of the true population? (ii) We can always do a ...
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8 views

Comparing abundance vs sites

I need to apply some basic stats to see if there are significant differences in total abundances of these three communities (X, Y and Z) with duplicate counts at three different locations (A, B and ...
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6 views

Weighting, standardize, transforming data before for Multivariate ANCOVA

My question is in regards to data manipulation prior to Multivariate ANCOVA. My research focuses on crustacean eggs. The model involves a covariate and 2 x independent variables and 4 dependent ...
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1answer
31 views

Stata ANOVA Interaction term differences

The following two statements produce different results. ...
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8 views

Analysis of proportional data (Two-factor design)

I did an experiment looking at damage to marine organisms as a result of fishing. I sampled in three vessels A, B and C. In each vessel I sampled the catch before on-deck handling (Pre) by fishermen ...
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1answer
41 views

Using F-tests for variance in non-normal populations

I'm fairly new to stats, so please excuse me if this problem is hopelessly elementary or misinformed. Basically, I'm wondering if you can help me understand whether I'm using the F-Test for variance ...
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Is Fisher's LSD as bad as they say it is?

When we perform experiments (on small sample sizes (usually the sample size per treatment group is about 7~8)) on two groups, we use a t-test to test for difference. However, when we perform an ANOVA ...
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44 views

How can I make 2-way ANOVA (Type I, II and III) with R?

I have the following data with factor 1 (A, B and C) and factor 2 (D and E): $$ \begin{array}{ccc} \hline & D & E\\ \hline A & 68 & 59\\ & 65 & 57\\ & 63 & 54\\ ...
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Follow up a significant interaction in ANOVA with dichotomous variables

Hopefully this is an easily answerable question, though I've been searching for an answer without any luck. I've run a 2x2x2x2 mixed-design ANOVA with two within-subjects and two between-subjects ...
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1answer
43 views

Is two-factor ANOVA without replication appropriate for my application?

I want to analyze results from a computer simulation in which I will vary two factors: (1) fan location, and (2) fan flow rate. After the simulation, I will query the results for gas concentrations ...
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Nested ANOVA in SPSS / Science Education

I am analyzing student performance on a pre/post test designed to assess gains for a week long high school biology curriculum on natural selection. After comparing pre/post performance using a ...
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1answer
40 views

Performing ANOVA/Regression on Percentage Data

I'm trying to see if there are any significant differences in 3 data sets that I have. The data is taken from around 1000 participants, each within different families who tried an experiment to see ...
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1answer
57 views

When should I use FDR or Bonferroni in multiple comparisons?

I have the following situations : (1) Very large number of variables - say 100 variables and 200 samples (observations). Although level of each variable is just 2 or 3 or 4 max. I am doing linear ...
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1answer
55 views

Doing post-hoc after a not significant interaction in mixed ANOVA

I conducted a mixed design ANOVA with two within-subjects factors: FactorA (2 levels), FactorB (2 levels), and one between-subjects factor: Group (2 levels). My main hypothesis regards the interaction ...
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42 views

F-ratio in repeated-measures ANOVA

In factorial designs with one random factor and one fixed factor, the expected mean square for the fixed factor does contain three sources: the main effect, the interaction, and error Therefore, to ...
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23 views

Analysis of repeated treatment design (Linear panel model vs. ANOVA)

General information Assume you have the following quasi-experimental repeated treatment design (T = Treatment, M = Measurement): ...
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1answer
32 views

ANOVA and finding differences between multiple groups over time

I was given a dataset to analyze with two factors, time and treatment, and one continuous dependent variable. Since the same individuals were measured at multiple times, technically it probably could ...
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1answer
46 views

Likert item as independent variable for ANOVA?

I am trying to analyze data based on a sample size of around 50 and would appreciate advice on which statistical test would be most appropriate. Participants, on a single questionnaire, were asked to ...
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1answer
29 views

Repeated measures paired test

I have the following data: 2 conditions - experimental & control. 20 participants, each having 3 results for each condition. Like in the following table: ...
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1answer
17 views

Help comparing two data sets. Methods

I have a set of data from two nights worth of monitoring. The monitoring picks up how busy a server is in terms of the number of threads processing. A change has been made and we want to analyse if ...
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1answer
50 views

Nonparametric ANOVA with interaction?

Is there any nonparametric version of ANOVA able to deal with multiple factors AND evaluate their interaction(s)? If the interactions are really impossible to evaluate, is there any generalization of ...
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2answers
72 views

Repeating many ANOVA tests with a large number of factors

I have a large number of factors that categorize my numerical observations in different ways and no preconception which if any of these factors may be significantly explanatory, but I have a p-value ...
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1answer
52 views

2x2 ANOVA - assess violations of homoscedasticity & normality

I have a 2x2 factorial unbalanced between-subject design, n = 355. My DV is a subjective probability estimate (i.e., a number between 0 and 100). My ANOVA model: ...
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Covariates in Repeated Measures ANOVA

I have made a repeated measures ANOVA which I have two independent variables, three covariates which I will calculate the effects individually for my thesis. I basically conducted two tasks with the ...
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14 views

simulate ANOVA data to follow a specific eta-squared

I am simulating RM-ANOVA data with three treatment conditions (one-way within subjects designs). I would like to be able to add an effect to the data so that eta-squared has a specific value. ...
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12 views

ANOVA - comparing rows with replicates

I have a situation where I want to test for differences between rows and columns in my data frame: ...
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1answer
64 views

Why do means&error bars in an ANOVA graph depend on the factors and covariates that define it?

I have a mixed-model design with between-subjects factors Group (treatment, control) and Difficulty (easy, hard), and within-subjects factor Timepoint (pre, post). I want to use my statistical package ...
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14 views

How to compute the Greenhouse-Geisser Epsilon for the interaction term of the 2 repeated factors in a Repeated Measures ANOVA

I’m trying to implement a program in C# to get the Greenhouse-Geisser Epsilon for a 2 factor ANOVA design with 3 levels each factor. Following the procedure on ...
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13 views

question on plotting error values for treatment effects from multiple regression output

Say I have some data, where a dependent variable, dv, is a function of some independent variable, iv, and a categorical ...
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2answers
19 views

What are correlations among between test statistics in multiple comparison procedures

In the book Multiple Comparisons Using R Bretz et al write that their R package multcomp improves power above other multiple comparison procedures by "accounting for the structural correlations ...
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Perfom a one-way ANOVA using rpsychi (R) and the subsequent post-hoc pair-wise comparisons [migrated]

I have 4 samples, represented by their means and standard deviations. If I consider a sample size for all of them as 100, how can I perform a one-way ANOVA using the library of rpsychi in R? The ...
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1answer
42 views

Interpreting the ANOVA output for hierarchical linear regression

I followed this tutorial to learn Hierarchical Linear Regression (HLR) in R, but couldn't understand how to interpret its sample output of ...
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1answer
101 views

What type of Research Design?

In an experiment, 25 subjects (Group A) are assigned to play an adventure game (with audio and non-audio) while another 25 subjects (Group B) are assigned to play a strategy game (with audio and ...
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43 views

Using repeated measures anova: Am I right?

We have just finished an experiment, where we had samples distributed into 6 groups and each group receiving a different treatment. Each group had 5 samples, with 20 replicate measurements taken per ...
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24 views

Calculating sample size. Repeated measures within subject

I'm trying to calculate the sample size for a repeated measures within subject experiment. I'm going to test the subjects under 4 conditions and for each condition 6 measurements are taken at ...
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2answers
36 views

Difference between Research Design and Experimental Design

What is the difference between Research Design and Experimental Design? I can't see any difference. Both of them need to establish Causality. Both of them are the arrangement for collection and ...
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40 views

How to: repeated measures anova and Friedman's test with multiple imputations for missing data

I have a study where patients were measured pre-operatively (time_pre), post-operatively (time_post) and long-term follow-up (time_lt). I have 60 subjects. Data consists of: 5 scale variables ...
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1answer
35 views

Why is this result not significant?

I am reading a research paper about the relationship between service quality and consumer behavior. One hypothesis is: customers experiencing no service problems have the strongest levels of favorable ...