tDistriQuantile
Declaration: 
tDistriQuantile (p: double; df: integer): double; 
The function tDistriQuantile returns the value of the quantile of the tdistribution for a given probability p, and a specified number of degrees of freedom ix. The parameter p may take any value in the open interval (0,1). The parameter ix may take values between 1 and MaxInt. If tDistriQuantile is called using invalid arguments a value of 0.0 is returned.

Hint 1: 
The calculated value is exact to about 8 significant figures. 
Hint 2: 
The function tDistriQuantile calculates the quantile by using the integral from 0.0 to the t value. This differs from the convention of how the integral of the t distribution is used in many statistical packages, which tabulate the integral between +infinity and the t value. Thus you have to use 1p to get comparable results. For example, in order to calculate the function TINV(p,df) of Microsofts Excel® you have to use tDistriQuantile(1p,df).

