I will try to correct some common misconceptions. There is still a confusing conflation in this thread between statistical significance and clinical siignificance. In large studies it is possible to show statistical significance (a.k.a. confidence) of a treatment effect whose benefit is so small that it is clinically of little significance (a.k.a. unimportant). It small studies, it is very common, and unfortunately often published, that no statistical significance is found (p>0.05) in a study when careful reading of the confidence interval shows that clinically significant (important) effects have not yet been excluded. In one recent study I read, the authors cited confidence intervals of 0.4 to 20 as the relative odds of the proposed versus the standard treatment causing harm. Since these confidence interval included 1, they stated "no significant difference between the two treatments." A 20 fold increase in complications is certainly clinically important! The proper interpretation of that experiment should not be "showed no difference" but read "our experiment was woefully inadequate to detect important differences, and therefore showed nothing." The difference is type I and type II error in statistics. See: http://www.musc.edu/dc/icrebm/statisticalsignificance.html The proper method is to define some level of difference in therapy you would consider important, then use Type II statistics to see if you can prove, with adequate confidence, that you have shown any actual difference in treatments must be less than that threshold. Beware, if you do that, you will be less likely to be able to publish some nonsensical article which really showed nothing but gets on your resume anyhow. A useful way to debunk this error is to ask anyone asserting that they found "no difference" what sort of difference they could have detected." If they can't answer that reasonably, they didn't analyze it correctly. At 100 yards without my glasses, my myopic eyes can't tell the difference between Hillary Clinton, Arnold Schwarzenegger and Shaquille O'Neal. My inability to show or detect a visual difference should not be interpreted as proving no difference exists. Kevin Powell MD PhD FAAP [log in to unmask] Saint Louis Children's Hospital For more information, send mail to [log in to unmask] with the message: info PED-EM-L The URL for the PED-EM-L Web Page is: http://www.brown.edu/Administration/Emergency_Medicine/ped-em-l.html