Student's tdistribution is a probability distribution for estimating the mean of a normally distributed population when the sample population is small. The distribution is used for many types of statistical studies, but primarily in linear regression analysis and for the Student ttests in assessing difference between two sample means. Given the often complex equations which govern such functions Texas Instruments has a line of graphing calculators with these functions preprogrammed for easy use. Tdistribution is one of several distribution models available on the TI84.
Things You'll Need
 TI84 graphing calculator

Turn the calculator on with the "ON" button, the bottom button on the left side.

Press the "2nd" button, the blue button located on the top left of the calculator.

Press the "VARS" button, located second from the right and directly below the direction buttons near the top. This brings up the "DISTR" function.

Scroll down to and select the fifth option "tcdf" (t cumulative probably distribution function).