Posts Tagged ‘ nonparametric ’

Correlation scatter-plot matrix for ordered-categorical data

April 7, 2010
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Correlation scatter-plot matrix for ordered-categorical data

When analyzing a questionnaire, one often wants to view the correlation between two or more Likert questionnaire item’s (for example: two ordered categorical vectors ranging from 1 to 5). When dealing with several such Likert variable’s, a clear presentation of all the pairwise relation’s between our variable can be achieved by inspecting the (Spearman) correlation matrix (easily achieved in R...

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Siegel-Tukey: a Non-parametric test for equality in variability (R code)

February 22, 2010
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Daniel Malter just shared on the R mailing list (link to the thread) his code for performing the Siegel-Tukey (Nonparametric) test for equality in variability. Excited about the find, I contacted Daniel asking if I could republish his code here, and he kindly replied “yes”. From here on I copy his note at full. p.s: (The R function can be downloaded from...

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Post hoc analysis for Friedman’s Test (R code)

February 22, 2010
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Post hoc analysis for Friedman’s Test  (R code)

My goal in this post is to give an overview of Friedman’s Test and then offer R code to perform post hoc analysis on Friedman’s Test results. (The R function can be downloaded from here) Preface: What is Friedman’s Test Friedman test is a non-parametric randomized block analysis of variance. Which is to say it is a non-parametric version of...

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