outliers (version 0.13-3)

cochran.test: Test for outlying or inlying variance

Description

This test is useful to check if largest variance in several groups of data is "outlying" and this group should be rejected. Alternatively, if one group has very small variance, we can test for "inlying" variance.

Usage

cochran.test(object, data, inlying = FALSE)

Arguments

object

A vector of variances or formula.

data

If object is a vector, data should be another vector, giving number of data in each corresponding group. If object is a formula, data should be a dataframe.

inlying

Test smallest variance instead of largest.

Value

• A list with class htest containing the following components:
• statistic
  the value of Cochran-statistic.
• p.value
  the p-value for the test.
• alternative
  a character string describing the alternative hypothesis.
• method
  a character string indicating what type of test was performed.
• data.name
  name of the data argument.
• estimate
  vector of variance estimates

Details

The corresponding p-value is calculated using pcochran function.

References

Snedecor, G.W., Cochran, W.G. (1980). Statistical Methods (seventh edition). Iowa State University Press, Ames, Iowa.

See Also

qcochran

Examples

set.seed(1234)
x=rnorm(100)
d=data.frame(x=x,group=rep(1:10,10))
cochran.test(x~group,d)
cochran.test(x~group,d,inlying=TRUE)
x=runif(5)
cochran.test(x,rep(5,5))
cochran.test(x,rep(100,5))