IDL Reference Guide: Procedures and Functions

## 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.

### 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

### 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
```

### Version History

 4 Introduced