270 search results for "anova"

Two-way analysis of variance: two-way ANOVA in R

August 7, 2009
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The one-way analysis of variance is a useful technique to verify if the means of more groups are equals. But this analysis may not be very useful for more complex problems. For example, it may be necessary to take into account two factors of variability to determine if the averages between the groups depend on the group classification...

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Analysis of variance: ANOVA, for multiple comparisons

July 30, 2009
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Analysis of variance: ANOVA, for multiple comparisonsThe ANOVA model can be used to compare the mean of several groups with each other, using a parametric method (assuming that the groups follow a Gaussian distribution).Proceed with the following example:The manager of a supermarket chain wants to see if the consumption in kilowatts of 4 stores between them are equal. He...

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Analysis of variance: ANOVA, for multiple comparisons

July 30, 2009
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Analysis of variance: ANOVA, for multiple comparisonsThe ANOVA model can be used to compare the mean of several groups with each other, using a parametric method (assuming that the groups follow a Gaussian distribution).Proceed with the following example:The manager of a supermarket chain wants to see if the consumption in kilowatts of 4 stores between them are equal. He...

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Repeated Measures ANOVA using R

March 9, 2009
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Repeated Measures ANOVA using R

While so-called “between-subjects” ANOVA is absolutely straightforward in R, performing repeated measures (within-subjects) ANOVA is not so obvious. I have come across at least three different ways of performing repeated measures ANOVA in R. Which method you use depends on … Continue reading →

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Analysis of Variance (ANOVA) using R

February 5, 2009
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Analysis of Variance (ANOVA) using R

I found some useful websites showing examples of how to use R for various sorts of ANOVA (between, within, mixed designs, etc): Using R for Psychological Research Quick-R for SAS/SPSS/Stata users enjoy

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Comrades Marathon: A Race for Geriatrics?

July 22, 2014
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Comrades Marathon: A Race for Geriatrics?

It has been suggested that the average Comrades Marathon runner is gradually getting older. As an “average runner” myself, I will not deny that I am personally getting older. But, what I really mean is that the average age of all runners taking part in this great event is gradually increasing. This is not just

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Guns are cool – time effects

July 19, 2014
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Guns are cool – time effects

September last year I made a post using the shootingtracker data. It is attempted in shootingtracker to register all shootings with at least four victims, be they wounded or dead. The data starts  January 1st 2013, which means that by now the...

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“Vignettes” Update

July 14, 2014
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“Vignettes” Update

As a follow-up to my post about major changes to FSA and that some of the “old” vignettes are now out-of-date, here is a brief summary of new material in the draft book chapters (linked to below) that replaced the … Continue reading →

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Upcoming R Training Course in Boston

June 18, 2014
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Upcoming R Training Course in Boston

R for Software Developers and Data Analysts Saturday June 28, 2014 9:00am-4:00pm Microsoft NERD, Cambridge, MA I’ll be presenting a one day professional development workshop on R programming for software developers and data scientists, sponsored by the Greater Boston Chapter of … Continue reading →

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Example 2014.6: Comparing medians and the Wilcoxon rank-sum test

June 12, 2014
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Example 2014.6: Comparing medians and the Wilcoxon rank-sum test

A colleague recently contacted us with the following question: "My outcome is skewed-- how can I compare medians across multiple categories?" What they were asking for was a generalization of the Wilcoxon rank-sum test (also known as the Mann-Whitney-Wilcoxon test, among other monikers) to more than two groups. For the record, the answer...

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