# st: Re: one-tail test

 From Christopher F Baum To statalist@hsphsun2.harvard.edu Subject st: Re: one-tail test Date Mon, 11 Oct 2004 09:45:20 -0400

```On Oct 11, 2004, at 2:33, Levy wrote:

```
```  How can i perform a one sided test after a linear regression?

after this regression
regress y x1 x2
i want to test if the coefficient of x2 is greater than 0
```
Presuming that the test statistic is of the positive persuasion, divide the reported p-value in half. E.g.

headroom | -659.463 484.5101 -1.36 0.178 -1625.788 306.8619

This test would be insig. at 10% level or better as a two-tailed test, but

. di ttail(74,1.36)
.08897949

indicates that a t of this (absolute) magnitude would allow us to test that the coeff is negative with a significance level of 91+%, that is, signif. at ten percent level as a one-tailed test.

Kit Baum, Boston College Economics baum@bc.edu
http://ideas.repec.org/e/pba1.html

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