If you can append the data in such a way that both parabolas are estimated
in the same analysis, you can use -testnl-
Al Feiveson
-----Original Message-----
From: Julie Mao [mailto:jmao@ualberta.ca]
Sent: Monday, April 21, 2003 8:32 PM
To: statalist@hsphsun2.harvard.edu
Subject: st: testing difference between maxima of 2 parabolas
Does anyone know how to test whether the maximum values of 2 parabolas (for
which the coefficients for x and x^2 were estimated from a regression) are
statistically different?
Given that a parabola takes the form:
y = (A * x) + (B * x^2), where A and B are the estimated
coefficients,
and given that the maximum of a parabola falls at:
x = A/(-2*B) [from setting the first derivative = 0],
and that I have the SE's for A and B for both parabolas... is there a way to
test whether the maximum from one parabola differs from that of another
parabola?
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