# sigma.test: One sample Chi-square test for a population variance In TeachingDemos: Demonstrations for Teaching and Learning

## Description

Compute the test of hypothesis and compute a confidence interval on the variance of a population.

## Usage

 ```1 2``` ```sigma.test(x, sigma = 1, sigmasq = sigma^2, alternative = c("two.sided", "less", "greater"), conf.level = 0.95, ...) ```

## Arguments

 `x` Vector of data values. `sigma` Hypothesized standard deviation of the population. `sigmasq` Hypothesized variance of the population. `alternative` Direction of the alternative hypothesis. `conf.level` Confidence level for the interval computation. `...` Additional arguments are silently ignored.

## Details

Many introductory statistical texts discuss inference on a single population variance and introduce the chi-square test for a population variance as another example of a hypothesis test that can be easily derived. Most statistical packages do not include the chi-square test, perhaps because it is not used in practice very often, or because the test is known to be highly sensitive to nonnormal data. For the two-sample problem, see `var.test`.

## Value

An object of class `htest` containing the results

## Note

This test is highly sensitive to nonnormality.

## Author(s)

G. Jay Kerns gkerns@ysu.edu

`var.test`, `print.htest`
 ```1 2``` ```x <- rnorm(20, mean = 15, sd = 7) sigma.test(x, sigma = 6) ```