prob_tcut {lessR}

Plot t-distribution Curve and Specified Cutoffs with Normal Curve

Description

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

Usage

prob_tcut(df, alpha=0.05, digits_d=3, y_axis=FALSE,
         fill="aliceblue", color_tail="palevioletred4",
         nrm_color=gray(.7), color_t=gray(.08),
         pdf_file=NULL, width=5, height=5, ...)

Arguments

df

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

alpha

Alpha to define the tail cutoff area.

digits_d

Number of decimal digits in the output.

y_axis

If FALSE, then the y axis is not displayed.

fill

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

color_tail

Color of the tail areas of the t-distribution.

nrm_color

Color of the normal curve.

color_t

Color of the t-distribution curve.

pdf_file

Name of the pdf file to which graphics are redirected.

width

Width of the pdf file in inches.

height

Height of the pdf file in inches.

...

Other parameter values for graphics.

Details

Replaces a t-table by providing the corresponding t-cutoff, the critical value based on the corresponding quantile, as well as a plot that illustrates the tail probabilities. Also compare to the standardized normal curve.

Value

cutoff: Cutoff-value, the corresponding quantile.

Author(s)

David W. Gerbing (Portland State University; [e-mail])

See Also

qt, pnorm.

Examples

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