Performs either a one sample chi-squared test to compare the variance of a vector with a given value or an F test to compare the variances of two samples from normal populations.

`VarTest(x, ...)`# S3 method for default
VarTest(x, y,
alternative = c("two.sided", "less", "greater"),
ratio = 1, sigma.squared = 1,
conf.level = 0.95, ...)

# S3 method for formula
VarTest(formula, data, subset, na.action, ...)

A list with class `"htest"`

containing the following components:

- statistic
the value of the F test statistic.

- parameter
the degrees of the freedom of the F distribution of the test statistic.

- p.value
the p-value of the test.

- conf.int
a confidence interval for the ratio of the population variances.

- estimate
the ratio of the sample variances of

`x`

and`y`

.- null.value
the ratio of population variances under the null.

- alternative
a character string describing the alternative hypothesis.

- method
the character string

`"F test to compare two variances"`

.- data.name
a character string giving the names of the data.

- x, y
numeric vectors of data values.

- 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.- ratio
the hypothesized ratio of the population variances of

`x`

and`y`

.- sigma.squared
a number indicating the true value of the variance, if one sample test is requested.

- conf.level
confidence level for the returned confidence interval.

- formula
a formula of the form

`lhs ~ rhs`

where`lhs`

is a numeric variable giving the data values and`rhs`

a factor with two levels giving the corresponding groups.- data
an optional matrix or data frame (or similar: see

`model.frame`

) containing the variables in the formula`formula`

. By default the variables are taken from`environment(formula)`

.- subset
an optional vector specifying a subset of observations to be used.

- na.action
a function which indicates what should happen when the data contain

`NA`

s. Defaults to`getOption("na.action")`

.- ...
further arguments to be passed to or from methods.

Andri Signorell <andri@signorell.net> (One sample test)

Two Sample test and help text from R-Core.

The formula interface is only applicable for the 2-sample tests.

The null hypothesis is that the ratio of the variances of the
populations from which `x`

and `y`

were drawn, or in the
data to which the linear models `x`

and `y`

were fitted, is
equal to `ratio`

.

`var.test`

, `bartlett.test`

for testing homogeneity of variances in
more than two samples from normal distributions;
`ansari.test`

and `mood.test`

for two rank
based (nonparametric) two-sample tests for difference in scale.

```
x <- rnorm(50, mean = 0, sd = 2)
# One sample test
VarTest(x, sigma.squared = 2.5)
# two samples
y <- rnorm(30, mean = 1, sd = 1)
VarTest(x, y) # Do x and y have the same variance?
VarTest(lm(x ~ 1), lm(y ~ 1)) # The same.
```

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