At 08:44 PM 6/20/2010, RICHARD M. HEIBERGER wrote:
You have only one Age value in each Lot. Hence the Age is aliased
with one of the
5 degrees of freedom between lots. You can see it in the picture
xyplot(Conc ~ Age|Lot, data=blots, pch=16)
There is no opportunity for a slope within each of the groups.
Rich
Doh!
Thanks.
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