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*.

*Note: *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.

## Examples

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

## Syntax

*Result* = T_CVF(*P*,* Df*)

## Return Value

Returns the cutoff value.

## Arguments

### P

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.

### Df

A positive integer, single- or double-precision floating-point scalar that specifies the number of degrees of freedom of the Student’s t distribution.

## Keywords

None

## Version History

4.0 |
Introduced |