# Squared ranks test

In statistics, the **Conover squared ranks test**[1][2] [3] is a non-parametric version of the parametric Levene's test for equality of variance. Conover's squared ranks test is the only equality of variance test that appears to be non-parametric. Other tests of significance of difference of data dispersion are parametric (i.e., are difference of variance tests). The squared ranks test is arguably a test of significance of difference of data dispersion not variance *per se*. This becomes important, for example, when the Levene's test fails to satisfy the rather generous conditions for normality associated with that test and is a default alternative under those conditions for certain statistical software programs like the VarianceEquivalenceTest[4] routine in Mathematica. In addition to Levene's test, other parametric tests for equality of variance include the Bartlett, Brown-Forsythe, and Fisher Ratio tests.

## References

- https://www.jstor.org/stable/2683975
- "ConoverTestâ€”Wolfram Language Documentation".
*Reference.wolfram.com*. Retrieved 2016-07-21. -
*SQUARED RANKS* - "VarianceEquivalenceTestâ€”Wolfram Language Documentation".
*Reference.wolfram.com*. Retrieved 2016-07-21.