In july 2008 the us national institutes of health announced that it was stopping a clinical study early because of unexpected results. the study population consisted of hiv-infected women in sub-saharan africa who had been given single dose nevaripine (a treatment for hiv) while giving birth, to prevent transmission of hiv to the infant. the study was a randomized comparison of continued treatment of a woman (after successful childbirth) with nevaripine vs. lopinavir, a second drug used to treat hiv. 240 women participated in the study; 120 were randomized to each of the two treatments. twenty-four weeks after starting the study treatment, each woman was tested to determine if the hiv infection was becoming worse (an outcome called virologic failure). twenty-six of the 120 women treated with nevaripine experienced virologic failure, while 10 of the 120 women treated with the other drug experienced virologic failure complete the hypothesis test and state an appropriate conclusion.