# Re: st: Testing equality of coefficients, linear and quadratic terms

 From Nick Winter To statalist@hsphsun2.harvard.edu Subject Re: st: Testing equality of coefficients, linear and quadratic terms Date Wed, 09 Nov 2005 22:21:25 -0500

```Neither.

You want, I think, a joint test that age1=age2 AND agesquare1=agesquared2

The -accum- option of test will let you construct this.

eg, using the auto dataset

gen mpgsq = mpg^2
gen f_mpg = foreign*mpg
gen f_mpgsq = foreign*mpgsq

reg price mpg mpgsq f_mpg f_mpgsq foreign
--output omitted--
test mpg = f_mpg
--output omitted--
test mpgsq = f_mpgsq, accum

( 1)  mpg - f_mpg = 0
( 2)  mpgsq - f_mpgsq = 0

F(  2,    68) =    3.02
Prob > F =    0.0554

--Nick Winter

At 09:15 PM 11/9/2005, you wrote:
```
```Hello,
I am familiar with the "test" procedure in Stata to
test for equality of coefficients across independent
samples, though have a question about the command. I
would like to test for equality of two coefficients
across samples, one for AGE and one for a square of
the AGE term (call it AGESQUARED). Basically I would
to determine if age curves are similar across samples,
incorporate the squared term. Which of the following
would be appropriate (if either)?

test AGE1 + AGESQUARED1 = AGE2 + AGESQUARED2

or

test AGE1 + (AGESQUARED1*AGESQUARED1) = AGE2 +
(AGESQUARED2*AGESQUARED2)

Dave

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