cvTest {asht}

Coefficient of Variation Test

Description

One-sample coefficient of variation tests and confidence intervals based on either normal or lognormal assumptions.

Usage

cvTest(x, nullCV = 1, 
alternative = c("two.sided", "less", "greater"), 
conf.level = 0.95, distn = c("normal", "lognormal"), 
CVmax = 10^6)

Arguments

x

numeric vector

nullCV

null coefficient of variation, or CV on boundary between null and alternative hypotheses

alternative

a character string specifying the alternative hypothesis, must be one of "two.sided" (default), "greater" or "less". You can specify just the initial letter.

conf.level

confidence level of the interval

distn

assumed distribution

CVmax

maximum coefficient of variation used in uniroot CI searches when distn='normal'

Value

A list of class 'htest'

statistic

mean

parameter

stadard deviation

estimate

estimate of coefficient of variation: sd(x)/mean(x) for distn='normal', and sqrt(exp(var(log(x)))-1) for distn='lognormal'

p.value

p.value associated with alternative

conf.int

confidence interval

null.value

null CV

alternative

alternative

method

description of method

Author(s)

Michael P. Fay

References

Koopmans, Owen, Rosenblatt (1964) "Confidence intervals for the coefficient of variation for the normal and log normal distributions" Biometrika 25-32.

Examples

cvTest(rnorm(25,mean=3,sd=.2),distn="normal")