[R] Selecting groups with R
David Winsemius
dwinsemius at comcast.net
Sat Aug 22 00:44:02 CEST 2009
On Aug 21, 2009, at 6:35 PM, jlwoodard wrote:
>
> Thank you David!
>
>
> David Winsemius wrote:
>>
>>
>> How.... did you do the "t-test"?
>>
>>
>
> t.test(Score,Color)
?t,test
t.test expects two numeric vectors, not a numeric vector and a
grouping indicator.
> t.test(dataset[dataset$Color=="RED", "Score"], dataset[dataset
$Color=="WHITE", "Score"] )
Welch Two Sample t-test
data: dataset[dataset$Color == "RED", "Score"] and dataset[dataset
$Color == "WHITE", "Score"]
t = -7.6485, df = 3.298, p-value = 0.003305
alternative hypothesis: true difference in means is not equal to 0
95 percent confidence interval:
-18.143205 -7.856795
sample estimates:
mean of x mean of y
11.66667 24.66667
>
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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