On Mon, 10 Apr 2000, dennis roberts wrote:
> the term 'null' does NOT mean 0 (zero) ... though it is misconstrued that way
Yes, and yes. I tend to switch to "nil" hypothesis to indicate that
special case of the null.
>
> 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 ...
Our current verbal lables leave much to be desired.
Depending on who you ask the "null hypothesis" is
a) a hypothesis of no effect (nil hypothesis)
b) an a priori false hypothesis to be rejected (straw dog hypothesis)
c) an a priori plausible hypothesis to be tested and falsified or
corroborated (wish I had a term for this usage/real null?)
The majority usage is consistant with cases a) and b) combined and there
is no clear usage that allows the seperation of case c) from the other
two. I have the bad habit of slipping back and forth between usages
hoping that the context will make clear my intent. I see that I have done
that in my message below. I have used "null" as a combination of cases a)
and c) in one spot and cases a) and b) in another. I plead early monday
syndrom.
>
> 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.
>
>
>
*******************************************************************
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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