[R] Problem: No p-value for a point-baserial correlation with R

Fox, John jfox at mcmaster.ca
Sat Apr 16 14:41:33 CEST 2016

Dear Dominik,

There's not enough information here to answer your question: You don't show the commands you used, nor the output that was produced, and you don't share your data. A good guess, however, is that there is only one level of the factor, perhaps after missing data are removed, and so it's not possible to compute a biserial correlation. 

By the way, if the dichotomous factor is really nominal, then it doesn't make sense to compute a biserial correlation, which assumes that there's a latent continuous and normally distributed variable that has been dichotomized at an unknown threshold.


John Fox, Professor
McMaster University
Hamilton, Ontario
Canada L8S 4M4
web: socserv.mcmaster.ca/jfox

From: R-help [r-help-bounces at r-project.org] on behalf of Dominik Maiori [d.maiori at windowslive.com]
Sent: April 16, 2016 5:39 AM
To: r-help at r-project.org
Subject: [R] Problem: No p-value for a point-baserial correlation with R

Dear community

I'm pretty new to R and I'm trying to do a Point-baserial correlation for a nominal dichotomous variable with a interval scaled variable. It works fine, but the output just shows me the correlation and nothing else (p-Value would be important).

I tried it with the following codes:

- biseral.cor()
- cor.biseral()
- I also tried a polyserial() I've found on this question page: http://stackoverflow.com/questions/35880910/point-biserial-and-p-value
Problem: It's not working (telling me y has fewer than 2 levels) and it would also be for a ordinal dichotomous variable, but I only have a nominal dichotomous variable.

In the forum if found following Syntax that I've tried out: https://stat.ethz.ch/pipermail/r-help/2003-April/031852.html
It seams to work because I don't get any error messages but I'm not getting an output either.

I'm really thankful for every help I could get on this topic or tips where I can find out and learn how to find a correlation with a p-value in R for a nominal dichotomous and an interval scaled variable.
Thanks in advance and have a nice weekend!

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