Computing T-Distribution Cumulative Probability Density Function

I’ll be the first to admit, its been a long time since I was in Statistics class, but it’s really one of the most useful classes out there, even the esoteric parts of it.

Recently, I had to write code to compute bias estimation for climate change data, and one of the key stats used in computing bias estimation along with its summary statistics is: the t-distribution cumulative probability density function, or tcdf for short.

In Java land, we are fortunate to have the Apache Commons Math library, which allows computation of tcdf and inverse-tcdf: 

Something like the following, using Apache Commons Math, will allow calculation of an inverse tcdf:

TDistribution t = new TDistributionImpl(degreeOfFreedom);
a = (t.inverseCumulativeProbability(0.975))


2 thoughts on “Computing T-Distribution Cumulative Probability Density Function

  1. Hi Victor,

    TDistributionImpl (packaged under the apache commons-math lib) can be imported from the class: org.apache.commons.math.distribution.TDistributionImpl

    If you are using Maven, include the Apache Commons Math library by adding the following to your pom.xml:


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