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Re: st: Mean Test

From   Maarten buis <>
Subject   Re: st: Mean Test
Date   Sun, 22 Jan 2006 19:26:42 +0000 (GMT)

Rijo wrote:
> But isn't  One way ANOVA also assume the equality of variance
> (of the populations) that we consider?. Hence in a case where 
> variances are statistically different would the method you
> suggest give the 'right' result?

Yes, anova assumes homogeneity of within-group variances (or if you are more regression oriented:
homoscedasticity). However, if you have a sufficient number of cases and the groups contain
approximately the same number of cases, than assuming equal variances won't do much harm, even
with moderate deviations from that assumption. Anyhow, it probably does less harm than doing
anova's/t-tests conditional on the results of a test for equality of variance. 


Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting adress:
Buitenveldertselaan 3 (Metropolitan), room Z214

+31 20 5986715

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