the term 'null' does NOT mean 0 (zero) ... though it is misconstrued that way
the term 'null' means a hypothesis that is the straw dog case ... for which
we are hoping that sample data will allow us to NULLIFY ...
in some cases, the null happens to be 0 ... but in many cases, it does not
cases in point:
1. null hypothesis is that the population variance for IQ is 225
2. null hypothesis is that the population mean for IQ is 100
3. to test the variance of a population ... the null is that the chi square
value will be degrees of freedom
and on and on and on
At 10:04 AM 4/10/00 -0500, Michael Granaas wrote:
>On Fri, 7 Apr 2000, dennis roberts wrote:
>
> > At 04:00 PM 4/7/00 -0500, Michael Granaas wrote:
> >
> > >But whatever form hypothesis testing takes it must first and formost be
> > >viewed in the context of the question being asked.
> >
> >
> > this seems to be the key to REinventing ourselves ... make sure the focus
> > is on the question ... AND, to REshape the question FROM what we
> > traditionally do in hyp test ...
>
>If you look at Psychology you might well see two traditions, one in which
>the zero valued null is used in a rather automatic and mindless fashion
>and another in which researchers work very hard setting up experiments
>where rejection of the zero valued null does provide some information.
>
> >
> > set up the null, etc. etc
> >
> > to ... ask the question of real interest ...
> >
> > what effect DOES this new treatment have?
> > what kind of correlation IS there between X and Y?
>
>In the second tradition I spoke of you find people asking exactly these
>types of questions once they have established that their experimental
>results are not due to chance. They use the hypothesis test as a step on
>the road to understanding, not as an end in and of itself.
>
>To me this second group acts more like model fitters (emphasis on
>prediction) than they do like hypothesis testers (emphasis on rejecting
>nil effects). Even though this second group rejects some nil valued
>hypothesis they, unlike the first, ask questions about things like effect
>size or functional form of an effect rather than simply declaring the
>effect is not zero and drawing some final conclusion.
>
>For myself I try to get students at all levels asking the types of
>questions that Dennis suggests as being obvious follow-ups to rejecting
>some nil hypothesis. I cannot claim a great deal of success, but I am
>trying.
>
> > what IS the difference between the smartness of democrats and republicans?
> >
> > if you ask questions that way ... they do not naturally or sensibly
> lead to
> > our testing the typical null hypotheses we set up
>
>Yes. There are a variety of answers to this problem, but, rejecting the
>no difference hypothesis when it is a priori false is not among them.
>
>Michael
>
>
> >
>
>*******************************************************************
>Michael M. Granaas
>Associate Professor [EMAIL PROTECTED]
>Department of Psychology
>University of South Dakota Phone: (605) 677-5295
>Vermillion, SD 57069 FAX: (605) 677-6604
>*******************************************************************
>All views expressed are those of the author and do not necessarily
>reflect those of the University of South Dakota, or the South
>Dakota Board of Regents.
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