|IDL Reference Guide: Procedures and Functions|
The T_CVF function computes the cutoff value V in a Student's t distribution with Df degrees of freedom such that the probability that a random variable X is greater than V is equal to a user-supplied probability P.
T_CVF computes the cutoff value using the one-tailed probability. The cutoff value for the two-tailed probability, which is the probability that the absolute value of X is greater than V), can be computed as T_CVF(P/2, Df).
This routine is written in the IDL language. Its source code can be found in the file
t_cvf.pro in the
lib subdirectory of the IDL distribution.
Result = T_CVF(P, Df)
Returns the cutoff value.
A non-negative single- or double-precision floating-point scalar, in the interval [0.0, 1.0], that specifies the probability of occurrence or success.
A positive integer, single- or double-precision floating-point scalar that specifies the number of degrees of freedom of the Student's t distribution.
Use the following command to compute the cutoff value in a Student's t distribution with five degrees of freedom such that the probability that a random variable X is greater than the cutoff value is 0.025.
result = T_CVF(0.025, 5) PRINT, result