Tagged Questions

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0answers
12 views

ANOVA as Comparision of Means and Regression [duplicate]

ANOVA, ANalysis Of VAriance, is a method to compare means of several variables. At the same time it falls under G(eneral)LM in a sense that it a method for regression and used for regressing ...
1
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0answers
17 views

Are the sequential sum of squares appropriate when treatments must be applied in sequence?

I'm working with some modeled future stream flow data that was created in two steps. First, future precipitation predictions (at certain points in a watershed) were created by running historical ...
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1answer
28 views

ANOVA determining percentage of variation

The Financial Review wished to estimate the amount of annual government spending using tax revenue and level of nationwide debt. Data from 1958-2008 (inclusive) was used. All variables were measured ...
3
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1answer
48 views

Dealing with outliers when comparing variances with Bartlett's test

I have four different groups (with unequal sample sizes of 100 to 120) and want to test if the variance differs. For ANOVAs I used the winsorized mean to get a more robust estimate and I am wondering ...
0
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1answer
32 views

What's the logic/motivation behind pre-filtering data based on variance?

I am currently working with gene expression data where I have a number of genes (variables) measured over a number of samples. I could not make sense of the statistics and visualization suite we have, ...
2
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2answers
133 views

Alternative to One-way ANOVA unequal variance

I would like to compare the means across three groups of equal sizes (equal sample size is small, 21). The means of each group are normally distributed, but their variances are unequal (tested via ...
1
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0answers
50 views

Variance associated with factors in GLS (nlme)

First time posting here, so thank you ahead of time for your help. I'd like to estimate the variances associated with two factors in a relatively simple, but unbalanced GLS model, and I am unsure how ...
0
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0answers
75 views

ANOVA and significance test for multiple groups

I am currently investigating the mousemove behavior of users while working different kind of searchtasks in wikipedia. I've isolated a certain number of move-flows and gathered data for each of them. ...
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0answers
60 views

finding the residual variance after correcting ordinal data for sex

I have a data set organized as: males, females as groups. Each individual has a "score" that is ordinal, ranking 0,1, or in another case, 0,1,2. I need to find the residual variation after correcting ...
1
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1answer
139 views

Explaining Variance

I am currently faced with the problem of explaining variance in an evaluation where users rate Cloud services on a quality scale. My data looks as follows: Dependent variable: Quality score (ratio ...
0
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0answers
47 views

Compare variability in different groups

I have 3 groups with a distribution of samples. I used ANOVA to compare means of these groups and also fetched mean, SD and SEM. I have SD and SEM that varies among groups. How can I compare them so ...
1
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0answers
56 views

Different Mean Square partitions in an unbalanced bifactorial ANOVA (with random factor) between R and Statistica

I am trying to extract variance components for selection and chance in a bifactorial design with Generation as a fixed factor and Replicate as a random term, for early fecundity. Since I am using ...
2
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1answer
34 views

Proper way to deal with several sources of variability

What is the proper way of combining various sources of variability? For example, if we know that under the normal conditions, a machine produces parts with normally distributed diameter with some ...
1
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1answer
260 views

R oneway.test with equal and non equal variance

can anybody tell me why the oneway.test() results in a p-value of NA when var.equal is set to FALSE but in a p-value of 0.7173 when it is set to TRUE Here is my ...
7
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0answers
1k views

How to estimate variance components with lmer for models with random effects and compare them with lme results

I performed an experiment where I raised different families coming from two different source populations, where each family was split up into a different treatments. After the experiment I measured ...
6
votes
4answers
770 views

Can I do a t test if I have little to no variance in one group?

I have 4 groups that I am comparing to a criterion. In one of my groups, all the participants answered the same on every item, i.e. there is no variance. How do I deal with that in my ANOVA? Also, ...
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1answer
178 views

Normalizing reading times using analysis of variance

I'm trying to compare gaze durations measured using an eye tracker for each word. Since longer words will naturally lead to longer gaze durations, simply comparing the values is inaccurate. ...
3
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2answers
233 views

Variance decomposition using ANOVA

Say you have a random variable $X$ (e.g., kilometers driven). Getting its variance is straightforward. But what if you want to say, $A$ percent of the variance in $X$ is due to $\text{Var}(X)$ for ...
3
votes
3answers
654 views

What is the difference between test to check homogenity of variance and ANOVA?

I found many tests like: Fligner, Levene etc etc to check homogeneity of variances, my question is: What is the difference between those tests and ANOVA ? Thank you
1
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1answer
569 views

How to deal with a non-gaussian distribution & heteroscedasticity

I am working on my thesis project and have come across a problem with the statistics which I am looking for a bit of guidance. I am running ANOVA tests to determine significance between groups but i ...
3
votes
1answer
444 views

Difference between homoscedastic and homogenic-variance data

I have a doubt regarding two tests: Breusch–Pagan test, to detect heteroscedasticity in a series, and Bartlett's test, to test for equal variances for samples from $k$ populations. What are the ...
4
votes
1answer
772 views

Effect size calculations in mixed ANOVA design for power analysis

I need to calculate effect size for a mixed ANOVA design. I need it because I'm using GPower3 to calculate a rough sample size for a full study. I have pilot data. Based on this page: ...
3
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2answers
833 views

Is there an anova procedure that doesn't assume equal variance?

When conducting a t-test we can always use a Welch approximation of the df, and let go of the assumption of equal variances. Is there something similar for (even one way) anova? (any R ...
4
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1answer
395 views

Variance components

I have a set of $N$ bodies, which is a random sample from a population whose mean and variance I want to estimate. A property of each body is being measured $m_i$ times ($m_i>1$) and different for ...