[R] another statistical question

[Peter Ehlers]

On 2011-03-31 07:44, Alexander Engelhardt wrote:
> Am 31.03.2011 15:46, schrieb Anna Lee:
>> Dear List!
>>
>> I have a unverse (basic population) which is not normally distributed.
>> Now from this universe I take some subsets. Each subset is normally
>> distributed within itself. I now want to compare the subsets and see
>> if they differ significantly. So what is my assumption - normal
>> distributed data and therefore comparison of means, or non normal
>> distributed data and therefore comparison of medians?
>
> If you want to do an ANOVA, the assumption is normality /within/ the
> groups. That is, Y given X=x is normal distributed. Also, you want the
> same variance within each group (group = your subset = factor value).

The equal-variances assumption is not strictly required.
R has the multiple-groups equivalent of the two-sample t-test.
See ?oneway.test.

Peter Ehlers

>
> Short answer: Means.
> (I am only 95% certain)
>
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