318 search results for "ANova"

Adonis (PERMANOVA) – Assumptions

April 26, 2011
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Adonis (PERMANOVA) – Assumptions

Before you use PERMANOVA (R-vegan function adonis) you should read the user notes for the original program by the author (Marti J. Anderson) who first came up with this method. An important assumtption for PERMANOVA is same "multivariate spread&qu...

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R Tutorial Series: 2011 ANOVA Article Data

March 28, 2011
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R Tutorial Series: 2011 ANOVA Article Data

Having wrapped up a recent flurry of R ANOVA articles (and exhausted my knowledge of the subject), I decided to take a look at the R Tutorial Series' Google Analytics data from the past few months. Since I posted the Two-Way Omnibus ANOVA article on J...

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R Tutorial Series: Applying the Reshape Package to Organize ANOVA Data

March 14, 2011
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R Tutorial Series: Applying the Reshape Package to Organize ANOVA Data

As demonstrated in the preceding ANOVA tutorials, data organization is central to conducting ANOVA in R. In standard ANOVA, we used the tapply() function to generate a table for a single summary function. In repeated measures ANOVA, we used separate da...

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R Tutorial Series: ANOVA Pairwise Comparison Methods

March 7, 2011
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R Tutorial Series: ANOVA Pairwise Comparison Methods

When we have a statistically significant effect in ANOVA and an independent variable of more than two levels, we typically want to make follow-up comparisons. There are numerous methods for making pairwise comparisons and this tutorial will demonstrate...

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Anova – Type I/II/III SS explained

March 2, 2011
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Anova – Type I/II/III SS explained

Not my post, just bookmarking this. It’s from http://goanna.cs.rmit.edu.au/~fscholer/anova.php ANOVA (and R) The ANOVA Controversy ANOVA is a statistical process for analysing the amount of variance that is contributed to a sample by different factors. It was initially derived by R. A. Fisher in 1925, for the case of balanced data (equal numbers of observations

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R Tutorial Series: Two-Way ANOVA with Unequal Sample Sizes

February 28, 2011
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R Tutorial Series: Two-Way ANOVA with Unequal Sample Sizes

When the sample sizes within the levels of our independent variables are not equal, we have to handle our ANOVA differently than in the typical two-way case. This tutorial will demonstrate how to conduct a two-way ANOVA in R when the sample sizes withi...

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R Tutorial Series: Two-Way Repeated Measures ANOVA

February 21, 2011
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R Tutorial Series: Two-Way Repeated Measures ANOVA

Repeated measures data require a different analysis procedure than our typical two-way ANOVA and subsequently follow a different R process. This tutorial will demonstrate how to conduct two-way repeated measures ANOVA in R using the Anova() function fr...

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R Tutorial Series: One-Way Repeated Measures ANOVA

February 14, 2011
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R Tutorial Series: One-Way Repeated Measures ANOVA

Repeated measures data require a different analysis procedure than our typical one-way ANOVA and subsequently follow a different R process. This tutorial will demonstrate how to conduct one-way repeated measures ANOVA in R using the Anova(mod, idata, i...

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R Tutorial Series: Two-Way ANOVA with Interactions and Simple Main Effects

February 7, 2011
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R Tutorial Series: Two-Way ANOVA with Interactions and Simple Main Effects

When an interaction is present in a two-way ANOVA, we typically choose to ignore the main effects and elect to investigate the simple main effects when making pairwise comparisons. This tutorial will demonstrate how to conduct pairwise comparisons when...

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Post-hoc Pairwise Comparisons of Two-way ANOVA

February 4, 2011
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Post-hoc Pairwise Comparisons of Two-way ANOVA

I read this post today by John Quick. I was a little taken back when he used a pairwise t-test for post hoc analysis. In a contradiction the t-test did not show differences in the treatment means when the ANOVA model did. This is because the pairwise.t.test does not take into account the two-way anova,

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