pgf: Graphical display for the F distribution, given a specified...

In bcdudek/bcdstats: A collection of functions to support B. Dudek's APSY510/511 classes

Graphical display for the F distribution, given a specified quantile

Description

A function to draw an F distribution and shade a region defined by the quantile. Note that pgf only gives upper tail probabilities and upper tail shading of the relevant area under the curve.

Usage

pgf(quantile, df1 = 1, df2 = 5)

Arguments

quantile	The quantile value (F value) to be evaluated.
df1	Numerator degrees of freedom for the F distribution. Note that the default is 1.
df2	Denominator degrees of freedom for the F distribution. Note that the default is 25.

Note

This function can be very helpful in instructional situations and can replace the "F table" from textbooks.

Warning: Specifying extremely high quantiles may not yield visible shaded areas if the quantile is in a region where the distribution approaches a density of zero.
In addition, probabilities are rounded to five decimal places and will display as zero if below .000005. Use the pf function in this case.

Note that the pgf function only displays upper tail regions since most inference with the F distribution only requires upper tail evaluation. The lower tail probability can be found as 1 minus the returned upper tail probability.

Author(s)

Bruce Dudek [e-mail]

Examples

pgf(3.75, df1=1,df2=25)
pgf(3.75, df1=2,df2=50)
pgf(3.75, df1=1,df2=125)
pgf(3.75, df1=6,df2=80)
pgf(4.11, df1=1,df2=18)
pgf(.65, df1=1,df2=25)

bcdudek/bcdstats documentation built on Sept. 29, 2024, 11:19 a.m.