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Re: Stats Power. Report Confidence Limits - p values

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  • Re: Stats Power. Report Confidence Limits - p values

    You are confusing something here. You dentist's 80% success rate (or the
    20% failure rate) has got nothing to do with your type I error
    probabilty. The alpha value reported in a statistical test would be the
    probablity that in 80% of the cases your dentist's patients would get
    better anyway, that is, assuming the null hypothesis that your dentist's
    treatment has no effect.

    So don't worry. You probably have a very good dentist.


    Bruce Etnyre, Ph.D., P.T. wrote:

    > Would anyone like to comment on clinical significance?
    > For example, my dentist can completely cure temporomandibular joint
    > dysfunction (TMJ) in 80% of patients by applying a plastic splint to
    > the teeth. Scientifically, this is not statistically significant. It
    > does not even approach statistical significance. So statistically we
    > would accept the null hypothesis that there is no difference in the
    > treatment of TMJ by using this device or not because the level of
    > confidence is only 80%.
    > Statistically, my dentist is a failure, but clinically, a world-beater!
    > BE
    > At 9:58 AM -0500 1/26/05, Dr. Chris Kirtley wrote:
    >> This brings up an interesting issue. I spoke to a statistician last
    >> year who
    >> told me that the only reason Fischer came up with these tables, and
    >> indeed the
    >> whole concept of significance testing, was because there were no
    >> computers
    >> available at that time. He considered T-tests, ANOVAs etc. to be stopgap
    >> methods that could to be used to get an approximate estimate until
    >> better
    >> computing power came along (as he expected it would).
    >> If Fischer were to be alive today, he would likely be appalled that
    >> we are
    >> still using his extremely simplified methods. Apparently any decent real
    >> statistician worth his salt these days performs a simulation in order to
    >> compute the likelihood of error. I was never able to find out how
    >> this is done,
    >> but perhaps someone else on the list can enlighten us? It really is
    >> time all of
    >> us in biomechanics moved into the modern age!
    >> Bryan Kirking wrote:
    >>> To comment and question some of Dr. Allison's insight:
    >>> >>My understanding of the arbitrary "line in the sand" of 0.05 was
    >>> >>originally due to the choice of the original tables (pre computer)
    >> --
    >> Dr. Chris Kirtley MD PhD
    >> Associate Professor
    >> Dept. of Biomedical Engineering
    >> Catholic University of America
    >> Washington DC 20064
    >> Alternative email:
    >> -----------------------------------------------------------------
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    >> For information and archives:
    >> -----------------------------------------------------------------
    > --
    > Bruce Etnyre, Ph.D., P.T.
    > Kinesiology Department
    > Professor and Chair
    > Rice University
    > 6100 Main MS 545
    > Houston, Texas 77005
    > USA
    > Phone: (713)348-5936 or 8816
    > FAX713)348-8808
    > -----------------------------------------------------------------
    > To unsubscribe send SIGNOFF BIOMCH-L to
    > For information and archives:
    > -----------------------------------------------------------------


    Prof. Dr. Nikolaus Troje
    Canada Research Chair
    in Vision and Behavioural Sciences
    Department of Psychology
    Queen's University
    Kingston, Ontario, K7L 3N6, CANADA

    phone: 613 533-6017
    fax: 613 533-2499


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