[cc'd to previous poster; please follow up in newsgroup] Robert J. MacG. Dawson <[EMAIL PROTECTED]> wrote in sci.stat.edu: >Stan Brown wrote: >> "The manufacturer of a patent medicine claims that it is 90% >> effective(*) in relieving an allergy for a period of 8 hours. In a >> sample of 200 people who had the allergy, the medicine provided >> relief for 170 people. Determine whether the manufacturer's claim >> was legitimate, to the 0.01 significance level."
> A hypothesis test is set up ahead of time so that it can only >give a definite answer of one sort. In this case, we have (at least) >three distinct possibilities. I really like your presentation of the three possible tests as "advertiser's test", "consumer advocate's test", and "quality controller's test". I see why the quality controller would want to do a two-tailed test: the product should not be outside manufacturing parameters in either direction. (Presumably the QC person would be testing the pills themselves, not patients taking the pills.) But I don't see why either the advertiser or the consumer advocate would, or should, do a two-tailed test. Alan McLean seemed to agree that both would be one-tailed, if I understand him correctly. > (1) The "consumer advocate's test": we want a definite result that >makes the manufacturer look bad, so H0 is the manufacturer's >claim, Ha is that the claim is wrong, and the p-value is to be used >as an indication of reason to believe H0 wrong (if so). Using a >one-sided test here is akin to saying "I want all my type I errors to be >ones that make the manufacturer look bad". Ethical behaviour here is to >do a two-sided test and report a result in either direction. I don't get this. Why is that ethical behavior? How I would analyze this claim is that, when the advertiser says "90% of people will be helped", that means 90% or more. Surely if we did a large controlled study and found 93% were helped, we would not turn around and say the advertiser was wrong! But I think that's what would happen with a two-tailed test. Can you explain a bit further? -- Stan Brown, Oak Road Systems, Cortland County, New York, USA http://oakroadsystems.com My reply address is correct as is. The courtesy of providing a correct reply address is more important to me than time spent deleting spam. ================================================================= Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =================================================================