I believe your interpretation is correct. The directionality of one-tailed tests leads to the definition of the p value. Let's suppose the alternative is that d>0, but you obtain a negative estimate for d. The p value is then everything under the pdf curve to the right of d. That is, 0.5 + (1 - the amount to the LEFT of the value of d). A similar case comes out of an alternative hypothesis of d<0, and you obtain a positive estimate for d. A pictorial representation of this should make this clearer, so just draw a Gaussian curve centered on 0, and put in some values for d, and then look at the part under the curve.
SteveDenham
... View more