On Sat, 1 Dec 2001 08:20:45 -0500, [EMAIL PROTECTED] (Stan Brown) wrote: > [cc'd to previous poster] > > Rich Ulrich <[EMAIL PROTECTED]> wrote in sci.stat.edu: > >I think I could not blame students for floundering about on this one. > > > >On Thu, 29 Nov 2001 14:39:35 -0500, [EMAIL PROTECTED] (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." > > >I have never asked that as a question in statistics, and > >it does not have an automatic, idiomatic translation to what I ask. > > How would you have phrased the question, then? Though I took this > one from a book, I'm always looking to improve the phrasing of > questions I set in quizzes and exams. [ snip, rest]
"In a LATER sample of 200 ... relief for ONLY 170 people." The Query you give after that should not pretend to be ultimate. Are you willing to ask the students to contemplate that the new experiment could differ drastically from the original sample and its conditions? "Is this result consistent with the manufacturer's claim?" - you might notice that this sounds 'weasel-worded.' Well, extremely-weasel-worded *ought* to be suiting, for *proper* statistical claims from non-randomized trials. For the example: I would expect 15% of a grab-sample being treated for 'allergy' would actually have flu or a cold. Maybe the actual experiment was more sophisticated? "What do you say about this result? (include a statistical test using a nominal alpha=.01)." Also, "Why do I include the word 'nominal' here?" Ans: It means 'tabled value' and it helps to emphasize that it is hard to frame a non-random trial as a test; the problem is not presented with any such framing. Hope this seems reasonable. -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html ================================================================= Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =================================================================
