Signal detection theory

[Robert Ariel]

Well, if you buy the assumptions of SDT you can.  Remember, SDT makes
assumption about behavior.  Specifically that decisions are made by applying
a decision criterion to the evidence extracted from each trial.   So, you
could conclude that one condition has a higher hit rate because that
condition has a larger bias toward saying yes in your experiment.  I guess
the question is, does it make theoretical sense to do so?

On Mon, Apr 19, 2010 at 7:33 AM, Tobias <tobias.fw at gmail.com> wrote:

> Thanks Robert,
>
> if I am not getting you wrong, this means that C is independent of d'
> but not of the hit rate.
> The question occurs to me if you can really say that one condition is
> more liberal if they are just better obviously.
>
> Cheers,
> Tobias
>
> On 16 Apr., 21:25, Robert Ariel <rar... at kent.edu> wrote:
> > Tobias,
> >
> > Computationally, C is the average of the your transformed hit and false
> > alarm rates.  You can see this in the equation you presented.  So, no
> doubt
> > if you have equal false alarm rates across conditions, differences in C
> are
> > resulting because of differences in hit rates.
> >
> > Basically with equal false alarm rates, the condition with a higher hit
> rate
> > will always be more liberal.  If hit rates are equal, the condition with
> > higher false alarm rate will be more liberal.
> >
> > Best,
> >
> > Robert
> >
> >
> >
> > On Fri, Apr 16, 2010 at 9:59 AM, Tobias <tobias... at gmail.com> wrote:
> > > Hi together,
> >
> > > this might be a bit off topic but as you are all very much into
> > > psychological experimental science you might be of great help for this
> > > issue. Besides, my topic is the outcome of an E-Prime experiment ;)
> >
> > > It is about the response bias in signal detection theory (SDT). I've
> > > heard that C is usually better than Beta as a measure of response bias
> > > as it is indpendent of d'. Now what I have in my experiment is a very
> > > high hit rate for condition A and a lower hit rate for condition B.
> > > False alarm rates are however the same for A and B. So what I get
> > > using the formula for C (C = -0.5*(z(false alarms) + z(hits)) is a
> > > liberal criterion C for A and a less liberal criterion for B.
> >
> > > So can I actually say that A is more liberal? Apparently this is only
> > > due to the fact that the hit rate is higher. I am quite puzzled by
> > > this... glad for any help!
> >
> > > Tobias
> >
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