[R] Calculating p-value for 1-tailed test in a linear model

[Rolf Turner]

On 20/08/11 10:20, Andrew Campomizzi wrote:
> Hello,
>
> I'm having trouble figuring out how to calculate a p-value for a 1-tailed
> test of beta_1 in a linear model fit using command lm.  My model has only 1
> continuous, predictor variable.  I want to test the null hypothesis beta_1
> is>= 0.  I can calculate the p-value for a 2-tailed test using the code
> "2*pt(-abs(t-value), df=degrees.freedom)", where t-value and degrees.freedom
> are values provided in the summary of the lm.  The resulting p-value is the
> same as provided by the summary of the lm for beta_1.  I'm unsure how to
> change my calculation of the p-value for a 1-tailed test.
>
> Thanks for your assistance,
>
> Andy

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     cheers,

         Rolf Turner