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*.

NoteT_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.

None

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

IDL prints:

2.57058

CHISQR_CVF, F_CVF, GAUSS_CVF, T_PDF

IDL Online Help (June 16, 2005)