iscamnormprob: Normal Tail Probability

In ISCAM: Companion to the Book "Investigating Statistical Concepts, Applications, and Methods"

Normal Tail Probability

Description

normprob finds a p-value and plots it onto a normal distribution with mean and standard deviation as specified. The function can find the probability above, below, between, or outside of the observed value, as specified by directions.

Usage

iscamnormprob(
  xval,
  mean = 0,
  sd = 1,
  direction,
  label = NULL,
  xval2 = NULL,
  digits = 4,
  verbose = TRUE
)

Arguments

xval	observed value.
mean	mean of normal distribution.
sd	standard deviation of normal distribution.
direction	direction for probability calculation, "above" or "below"; if "outside" or "between" are used, a second larger observation, xval2 must be specified
label	horizontal axis label.
xval2	second observation value.
digits	number of digits to display.
verbose	Logical, defaults to TRUE. Set to FALSE to suppress messages

Value

a p-value and a plot of the normal distribution with shaded area representing probability of the observed value or more extreme occurring.

Examples

iscamnormprob(1.96, direction = "above")
iscamnormprob(-1.5, mean = 1, sd = 2, direction = "below")
iscamnormprob(0, xval2 = 1.5, direction = "between")
iscamnormprob(-1, xval2 = 1, direction = "outside")

ISCAM documentation built on Feb. 12, 2026, 5:07 p.m.