Hi Rich,

It is a bit hard to read the "summary" you are using.  Consider please
pasting the output of:
ls.str(chemdata)

Regarding your question, please start and see if this work (I'm not sure,
since it seems you have made some changes to the summary output, and I am
only guessing how things look):
mean(chemdata$quant[chemdata$param =="Arsenic"])
sd(chemdata$quant[chemdata$param =="Arsenic"])


Cheers,
Tal


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On Wed, Aug 31, 2011 at 12:00 AM, Rich Shepard <rshepard@appl-ecosys.com>wrote:

> mean(chemdata.param="Arsenic")

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