normalityTest: Normality Tests

Description

Perform one of several tests of normality, either for a variable or for a variable by groups. The normalityTest function uses the shapiro.test function or one of several functions in the nortest package. If tests are done by groups, then adjusted p-values, computed by the Holm method, are also reported (see p.adjust).

Usage

normalityTest(x, ...)
# S3 method for formula
normalityTest(formula, test, data, ...)
# S3 method for default
normalityTest(x, 
    test=c("shapiro.test", "ad.test", "cvm.test", "lillie.test", 
        "pearson.test", "sf.test"),
    groups, vname, gname, ...)

Value

If testing by groups, the function invisibly returns NULL; otherwise it returns an object of class "htest", which normally would be printed.

Arguments

x: numeric vector or formula.
formula: one-sided formula of the form ~x or two-sided formula of the form x ~ groups, where x is a numeric variable and groups is a factor.
data: a data frame containing the data for the test.
test: quoted name of the function to perform the test.
groups: optional factor to divide the data into groups.
vname: optional name for the variable; if absent, taken from x.
gname: optional name for the grouping factor; if absent, taken from groups.
...: any arguments to be passed down; the only useful such arguments are for the pearson.test function in the nortest package.

Author

John Fox jfox@mcmaster.ca

Examples

Run this code

  data(Prestige, package="car")
  with(Prestige, normalityTest(income))
  normalityTest(income ~ type, data=Prestige, test="ad.test")
  normalityTest(~income, data=Prestige, test="pearson.test", n.classes=5)