| shapiro.test {stats} | R Documentation |
Performs the Shapiro-Wilk test of normality.
shapiro.test(x)
x |
a numeric vector of data values. Missing values are allowed, but the number of non-missing values must be between 3 and 5000. |
A list with class "htest" containing the following components:
statistic |
the value of the Shapiro-Wilk statistic. |
p.value |
an approximate p-value for the test. This is
said in Royston (1995) to be adequate for p.value < 0.1. |
method |
the character string "Shapiro-Wilk normality test". |
data.name |
a character string giving the name(s) of the data. |
The algorithm used is a C translation of the Fortran code described in Royston (1995) and found at http://lib.stat.cmu.edu/apstat/R94. The calculation of the p value is exact for n = 3, otherwise approximations are used, separately for 4 <= n <= 11 and n >= 12.
Patrick Royston (1982) An extension of Shapiro and Wilk's W test for normality to large samples. Applied Statistics, 31, 115–124.
Patrick Royston (1982) Algorithm AS 181: The W test for Normality. Applied Statistics, 31, 176–180.
Patrick Royston (1995) Remark AS R94: A remark on Algorithm AS 181: The W test for normality. Applied Statistics, 44, 547–551.
qqnorm for producing a normal quantile-quantile plot.
shapiro.test(rnorm(100, mean = 5, sd = 3)) shapiro.test(runif(100, min = 2, max = 4))