Description Usage Arguments Details Value Author(s) References Examples

Coefficient of Variation Test

1 | ```
CV.test(x1, x2, test = "F")
``` |

`x1` |
a numeric vector |

`x2` |
a numeric vector |

`test` |
the type of test to perform, "F" for a variance-ratio test or
"Z" for a |

`CV.test`

tests for the difference in coefficients of variations for
two variables (`x1`

and `x2`

), using either a variance ratio
(*F*) test (default) or a *Z* test.

The variance-ratio test was described by Lewontin (1966), but apparently
dates back to Wright (1952) and Bader and Lehman (1965). This test involves
a ratio of log-transformed variances, which follows an *F*-distribution
with *n1-1* and *n2-1* degrees of freedom.

Miller (1991) describes a *Z* test that does not involve a
log-transformation, provided that the data are positive and normally
distributed. The *Z* test performs best if the coefficients of
variation are less than 0.33.

`CV1, CV2 ` |
Coefficients of variation for |

`test` |
The type of test performed, "F" or "Z" |

`test.stat` |
The test statistic for |

`p` |
P-value for the test statistic |

Kevin Middleton ([email protected])

Bader, R.S. and W.H. Lehman. 1965. Phenotypic and genotypic
variation in odontometric traits of the house mouse. *American
Midlands Naturalist* 74: 28-38.

Lewontin, R.C. 1966. On the measurement of relative variability.
*Systematic Zoology* 15: 141-142.
http://www.jstor.org/stable/2411632

Miller, G.E. 1991. Asymptotic test statistics for coefficients of variation.
*Communications in Statistics-Theory and Methods* 20: 2251-2262.

Wright, S. 1952. The genetics of quantitative variability. *In:* Reeve,
E.C.R. and C. Waddington (eds.). *Quantitative Inheritance*. pp.
5-41. H.M.S.O., London.

Zar, J.H. 2010. *Biostatistical Analysis*. 5th Edition. Pearson
Prentice-Hall. Upper Saddle River, NJ. ISBN-10: 0131008463. ISBN-13:
978013100846.
http://www.pearsonhighered.com/educator/product/Biostatistical-Analysis/9780131008465.page

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