# TI-BASIC:Fpdf

**Command Summary**

Evaluates the F-distribution probability density function at a point.

**Command Syntax**

Fpdf(*x*, *numerator df*, *denominator df*)

**Menu Location**

Press:

- 2ND DISTR to access the distribution menu
- 8 to select Fpdf(, or use arrows.

Press 9 instead of 8 on a TI-84+/SE with OS 2.30 or higher.

TI-83/84/+/SE

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Fpdf( is the F-distribution probability density function.

Since the F-distribution is continuous, the value of Fpdf( doesn't represent an actual probability - in fact, one of the only uses for this command is to draw a graph of the distribution. You could also use it for various calculus purposes, such as finding inflection points.

The command takes 3 arguments: *x* is the point at which to evaluate the function (when graphing, use X for this argument), *numerator df* and *denominator df* are the numerator degrees of freedom and denominator degrees of freedom respectively (these specify a single Fpdf( curve out of an infinite family).

The F-distribution is used mainly in significance tests of variance.

# Formulas

The value of the Fpdf( is given by

Here, B is the [wikipedia:beta_function Beta function].