On Fri, 17 Jun 2005 04:53:07 -0700, "Anita"
wrote:

Yes the explanation of Ttest is very helpful thanks.

But, I still don't understand why I have an E-15 at the end of the answer.
If I change the number of decimal places to show 15 then I get a very small
number; does this therefore mean that the two means are different because the
value is significantly less than 0.05?

Assuming you have selected the ranges correctly, that's exactly what
it means.

(0.05 is not the only standard of comparison, but it's the most
common. Assuming the two data sets are random samples, the E-15 days
there's only about one chance in a thousand million million that the
difference in the data sets could have come about by chance. The
calculation of probability takes the sizes, averages, and scatter of
the data sets into account.

--
Stan Brown, Oak Road Systems, Tompkins County, New York, USA
http://OakRoadSystems.com
A: Maybe because some people are too annoyed by top-posting.
Q: Why do I not get an answer to my question(s)?
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?