The following post from the IV Board seems to agree that using the HR of subgroups at an interim look is a good way to determine the outcome at a final look. <a href="http://www1.investorvillage.com/smbd.asp?mb=971&mn=135382&pt=msg&mid=2368325" target="_blank">http://www1.investorvillage.com/smbd.asp?mb=971&mn=135382&pt=msg&mid=2368325</a>