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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.


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