# Posts Tagged ‘ non-parametric ’

## Correlation scatter-plot matrix for ordered-categorical data

April 7, 2010
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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...

## 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...

## Barnard’s exact test – a powerful alternative for Fisher’s exact test (implemented in R)

February 7, 2010
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(The R code for Barnard’s exact test is at the end of the article, and you could also just download it from here) About Barnard’s exact test About half a year ago, I was studying various statistical methods to employ on contingency tables. I came across a promising method for 2×2 contingency tables called “Barnard’s exact test“. Barnard’s test is a non-parametric alternative to Fisher’s exact...

## Non-parametric Methods

September 24, 2009
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A statistical method is called non-parametric if it makes no assumption on the population distribution or sample size. This is in contrast with most parametric methods in elementary statistics that assume the data is quantitative, the population...