lessR (version 2.2)

prob.t: Plot t-distribution Curve and Corresponding Normal Curve with Tail Cutoffs

Description

Plot a specified t-distribution against the standardized normal curve with the corresponding upper and lower tail cutoffs.

Usage

prob.t(df, alpha=0.05, dig.dec=3, y.axis=FALSE,
         col.fill="aliceblue", col.tail="palevioletred4",
         col.nrm=gray(.7), col.t=gray(.08), ...)

Arguments

df

Degrees of freedome for t-distribution, must be 2 or larger.

alpha

Alpha to define the tail cutoff area.

dig.dec

Number of decimal digits in the output.

y.axis

If FALSE, then the y axis is not displayed.

col.fill

Fill color for the interior of the t-distribution curve.

col.tail

Color of the tail areas of the t-distribution.

col.nrm

Color of the normal curve.

col.t

Color of the t-distribution curve.

...

Other parameter values for graphics.

Details

Replaces a t-table by providing the corresponding t-cutoff or critical value as well as a plot that illustrates the tail probabilities and also compared to the standardized normal curve.

See Also

pnorm, plot.

Examples

# t-distribution with 0.025 cutoffs for degrees of freedom of 15
prob.t(15)