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>  Docs Center  >  IDL Reference  >  Math - Probability  >  T_CVF

### T_CVF

T_CVF

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.

None

## Version History

 4 Introduced