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Hartley's and Cochran's testsfor homogeneity of varianceOn this page: Hartley's Fmax test Cochran's testHartley's F_{max} testHartley's F_{max} test is probably the simplest test of homogeneity of variances. It is not very sensitive to departures from homogeneity, but some statisticians (for example Winer The statistic F_{max} is calculated as the ratio of the largest and smallest variances of the (k) groups each containing (n) observations:
The observed value of F_{max} (with k and n1 degrees of freedom) is then compared with a table of critical values provided in a number of statistical texts (such as Winer Most tables are only for equal numbers of replicates, but Gill Hartley's F_{max} test assumes that the data for each group are normally distributed. It is apparently quite sensitive to violations of this assumption, so it should not be used on heavily skewed data.
Cochran's testCochran's test is another relatively simple homogeneity of variance test. It uses the ratio of the largest variance to the sum of the variances as the test statistic. Since it uses more information it is, not surprisingly, more powerful than Hartley's F_{max} test  at least for small equal sample sizes.
A table of critical values of C (with k and n1 degrees of freedom) is provided in Winer
