[R] p-value from GEE why factor 2*pnorm?
bcarvalh at jhsph.edu
Mon Jun 11 17:46:59 CEST 2007
Well, AFAIK, the definition of a p-value is the probability of
observing something at least as extreme as the observed data.
If you observed z, and Z follows a std-normal
p-value = P( Z < -abs(z) ) + P( Z > abs(z) )
= 2*P ( Z > abs(z) )
= 2*pnorm(z, lower.tail=FALSE)
try z=0 (you should get 1) and z=1.96 (you should get 5%)
On Jun 11, 2007, at 11:34 AM, Carmen Meier wrote:
> Benilton Carvalho schrieb:
>> the recommendation was to use lower.tail=FALSE.
> but then the results are significant and this does not match the
> The results are matching the observations if the formula is
> lower.tail =TRUE)
> so I have any unknown problem .... anywhere :-(
> REgards Carmen
More information about the R-help