var.test {stats} | R Documentation |

Performs an F test to compare the variances of two samples from normal populations.

var.test(x, ...) ## Default S3 method: var.test(x, y, ratio = 1, alternative = c("two.sided", "less", "greater"), conf.level = 0.95, ...) ## S3 method for class 'formula': var.test(formula, data, subset, na.action, ...)

`x, y` |
numeric vectors of data values, or fitted linear model
objects (inheriting from class `"lm"` ). |

`ratio` |
the hypothesized ratio of the population variances of
`x` and `y` . |

`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 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. |

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`

.

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. |

`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) y <- rnorm(30, mean = 1, sd = 1) var.test(x, y) # Do x and y have the same variance? var.test(lm(x ~ 1), lm(y ~ 1)) # The same.

[Package *stats* version 2.5.0 Index]