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Friday, June 24, 2011

Test for homogeneity of variance: Bartlett test

First an important assumption: that the normal distribution is followed by the data.
Null hypothesis for this test is that the variances are equal in the groups.
So if, p value less than 0.05, null hypothesis is rejected and interpretation being that the variances are not equal (or homodescacity is absent).

In case, the normality assumption is violated, then we can go for Levene test.

For further discussion using R: http://wiki.stdout.org/rcookbook/Statistical%20analysis/Homogeneity%20of%20variance

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