qgchisq: Graphical display for the Chi Squared distribution, given a...

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

Graphical display for the Chi Squared distribution, given a specified probability

Description

A function to produce a graph of a Chi Squared distribution with regions shaded according to a specified probability.

Usage

qgchisq(prob, df = 1)

Arguments

prob	The tail probability value to define the region to be shaded on the graph and the corresponding quantile to be displayed.
df	The df for the Chi Squared Distribution. Default is 1 df (see note below)

Warning

Specifying extremely high or low probabilities may not yield visible shaded areas if the regions are beyond the limits of the X axis scale of the graph.

Note

The scaling on plots of Chi Squared Distributions of varying degrees of freedom requires considerable adjustment. When df=1, qgchisq returns a two-paneled figure. The plot on the left is a fairly full scale plot of the distribution without shading of a tail region. The plot on the right has axes truncated so that scale expansion will permit visualization of the relevant area under the curve.

Also note that the qgchisq function only displays upper tail regions since most inference with the Chi Squared distribution only requires upper tail evaluation. The lower tail probability is 1 minus the returned value.

Author(s)

Bruce Dudek [e-mail]

See Also

pgchisq

Examples

qgchisq(.05,df=1)
qgchisq(.05,df=2)
qgchisq(.05,df=25)
qgchisq(.05,df=250)
qgchisq(.01,df=1)
qgchisq(.01,df=2)
qgchisq(.01,df=25)
qgchisq(.01,df=250)

bcdudek/bcdstats documentation built on Jan. 3, 2024, 10:09 p.m.