# Pearson’s chi-squared test: a simple implementation in R (test of independence)

December 17, 2014
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(This article was first published on The Beginner Programmer, and kindly contributed to R-bloggers)

Hi everyone! Today I found my old statistics workbooks and start wondering what I could get out of them.

Statistics can look pretty boring when using only pen and paper, since many times you’re just making a lot of repetitive calculations. However, the results of those calculations might of course be interesting.

Person’s chi-squared test is a simple test, as my professor put it, one of the first tests you should be performing when analysing a double entry table. You might be asking yourself why. Well, the answer is that this test looks for connection between the two variables in the table. As you might know connection is different from dependence. Dependence is of course a stronger bond and kind of a “one way bond” whilst connection is sort of a “double way bond”. If there’s no or little connection, then you might want to change variables in play since there is nothing but little interest in performing further tests on the same set of data.

Check on Wikipedia for more information on the theory.

Here is the R code I used to implement the test on the raw data at the bottom of the page.

Below is the output, it seems there’s a feeble connection between the two phenomena we studied.

The data I used for the simulation are available to be downloaded here.

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