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Gary  
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 More options Jul 2, 7:46 pm
Newsgroups: sci.stat.math
From: Gary <LanceG...@gmail.com>
Date: Thu, 2 Jul 2009 02:46:44 -0700 (PDT)
Local: Thurs, Jul 2 2009 7:46 pm
Subject: A test for discrete versus continuous?
This is a somewhat poorly formed question but the problem it
represents has troubled me several times in my career. Essentially
many theories may state that a particular phenomenon exists either as
a dimension or as a set of discrete categories. For example Reversal
Theory in psychology states (amongst other things) that a person is
either in a telic (purpose driven, arousal avoiding, future oriented)
mode or in a paratelic (activity driven, arousal seeking, present
oriented) mode and that people can't be somewhere "inbetween" the two
modes. So Reversal theory is positing a set of two discrete categories
and strongly claims that all people are in one or other of the two
states and that there is no continuum between them. Similarly Fulda
developed a mathematical model of the pull of temptation and asserts
that the model works on discrete moments of thought (in other words
the probabilities of temptation that are being modelled are discrete
and not continuous). In my experience it is really hard to devise
tests for claims of this kind. I wondered whther there are any
existing statistical tests designed to to test hypotheses of this
kind, or whether there are procedures and designs suitable for testing
such claims?

Lance


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illywhacker  
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 More options Jul 2, 11:47 pm
Newsgroups: sci.stat.math
From: illywhacker <illywac...@gmail.com>
Date: Thu, 2 Jul 2009 06:47:21 -0700 (PDT)
Local: Thurs, Jul 2 2009 11:47 pm
Subject: Re: A test for discrete versus continuous?
On Jul 2, 11:46 am, Gary <LanceG...@gmail.com> wrote:

Hi Lance,

These claims seem meaningless as scientific statements, unless there
is some way to relate the state someone is in to something measurable.
Obviously if you could measure the state directly, then in the two-
state case you would only ever see two outcomes, which seems pretty
clear cut. So I presume the state is inferred from some other form of
measurement. What would that be?

illywhacker;


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Ray Koopman  
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 More options Jul 3, 1:25 am
Newsgroups: sci.stat.math
From: Ray Koopman <koop...@sfu.ca>
Date: Thu, 2 Jul 2009 08:25:24 -0700 (PDT)
Local: Fri, Jul 3 2009 1:25 am
Subject: Re: A test for discrete versus continuous?
On Jul 2, 2:46 am, Gary <LanceG...@gmail.com> wrote:

Look up 'taxometrics', which claims to be able to identify discrete
phenomena. I don't think it can, but many people do.

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aruzinsky  
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 More options Jul 3, 1:27 am
Newsgroups: sci.stat.math
From: aruzinsky <aruzin...@general-cathexis.com>
Date: Thu, 2 Jul 2009 08:27:39 -0700 (PDT)
Local: Fri, Jul 3 2009 1:27 am
Subject: Re: A test for discrete versus continuous?
On Jul 2, 3:46 am, Gary <LanceG...@gmail.com> wrote:

In some instances a phenomenon is finely discrete, e.g., an integer,
instead of continuous, e.g., a real number.  Let's just call both
cases "practically continuous."  The first thing that you need to do
define a practically continuous metric, make measurements with this
metric, and plot a histogram.  If the histogram has gaps larger than
the discretization of the metric, the phenomenon is not practically
continuous.

For example, to measure schizophrenia, one might construct a
practically continuous metric Yj = sum Ai/Bi, i = 1 to N

where

N = Number of false beliefs that a jth individual has

Ai = Strength of conviction (certainty) for ith false belief

Bi = Proportion of population with ith (identical) false belief (to
reduce the influence of mass delusions from popular religions and
Obama)

Then you make measurements on many individuals and plot the
histogram.  If the histogram has big gaps, the schizophrenia is not
practically continuous.  You can bet it would be bell shaped like that
of IQ.  Of course, you have to know which beliefs are false to measure
their number.  So, dumb F psychologists without thermometers classify
things as hot or cold.


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Ray Koopman  
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 More options Jul 3, 1:47 am
Newsgroups: sci.stat.math
From: Ray Koopman <koop...@sfu.ca>
Date: Thu, 2 Jul 2009 08:47:48 -0700 (PDT)
Local: Fri, Jul 3 2009 1:47 am
Subject: Re: A test for discrete versus continuous?
[Second try -- the first seems to have gotten lost.]

On Jul 2, 2:46 am, Gary <LanceG...@gmail.com> wrote:

Look up 'taxometrics', which claims to be able to identify discrete
phenomena. I don't think it can, but many people do.

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kunzmilan  
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 More options Jul 3, 6:11 pm
Newsgroups: sci.stat.math
From: kunzmilan <kunzmi...@atlas.cz>
Date: Fri, 3 Jul 2009 01:11:31 -0700 (PDT)
Local: Fri, Jul 3 2009 6:11 pm
Subject: Re: A test for discrete versus continuous?
On 2 čnc, 11:46, Gary <LanceG...@gmail.com> wrote:

Your post is an example of discrete. A symbol, a word, a sentence
either exists, and can be counted, or it is not present at all.
Discrete occurences can be tested and evaluated as discrete, e.g. by
Poisson distribution. When occurences are numerous, this distribution
transforms into continuous distribution.
kunzmilan

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illywhacker  
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 More options Jul 3, 7:28 pm
Newsgroups: sci.stat.math
From: illywhacker <illywac...@gmail.com>
Date: Fri, 3 Jul 2009 02:28:29 -0700 (PDT)
Local: Fri, Jul 3 2009 7:28 pm
Subject: Re: A test for discrete versus continuous?
On Jul 2, 5:47 pm, Ray Koopman <koop...@sfu.ca> wrote:

I agree with you! Don't these people take 'Scientific Method 101'
before they are let loose on patients?

illywhacker;


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Gary  
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 More options Jul 3, 10:30 pm
Newsgroups: sci.stat.math
From: Gary <LanceG...@gmail.com>
Date: Fri, 3 Jul 2009 05:30:09 -0700 (PDT)
Local: Fri, Jul 3 2009 10:30 pm
Subject: Re: A test for discrete versus continuous?

I just tried to give some examples - but obviously they were very
brief without any defence of the ideas. I don't think the sort of
question I was posing is unique to psychology - I'm not a physicist
but my memories of high school physics include the idea of quanta and
that electrons had to choose particular distances from nuclei, and the
like, so the same kind of question occurs elsewhere in other
subjects.

In reversal theory (the example I started with) the argument is pretty
common sense really. It is the idea that we experience the content of
our minds and the feelings our body generates in discrete but bi-
stable ways. So when you are relaxing in the evening you might not
mind that nothing much is happening - you will take that as
pleasureable and not seek arousal and not be worried that your goals
are not being achieved. But there are other occasions when the same
absense of stimulation is experienced as boredom, and you feel you
should be doing something and accomplishing something and you worry
about achiving larger goals. I could go on but there is a great deal
of data to support the idea that different approaches to mental
content can exist in the same individual at different times. The
theory claims that the meta states (discrete, notice) are bi-stable
and quite abrupt switches can occur between them. You are, for
example, a thrill seeker and love riding on a roller coaster, and when
on a roller coaster you enjoy the arousal that the experience
provides. But imagine looking forward across the approaching dip in
the roller coaster ride and noticing a break in the rails. Suddenly
your enjoyment of the arousal can turn to an extremely unpleasant
experience of arousal - fear and anxiety. The same mental content
(high arousal) but experienced differently.

Phenomenologically most people find reversal theory quite convincing
(try to read some of the appers and see for your self). Obviously
there are measurable things involved - arousal level can be measured,
so can "hedonic tone" (heck that dates back to Wundt) and the like.
But to test reversal theory one would need to rule out the middle
ground. One would need to show that high levels of arousal cannot be a
matter of indifference for a person - they must be experienced as
something pleasant (exciting, thrilling, exhilirating) or as something
unpleasant (anxiety, fear, dread, shock, etc). So one needs to show
that there is not a continuum in the way people experience high
arousal but rather two discrete ways in which the mental content and
feelings can be taken. Similar remarks can be made for low arousal
levels (very low arousal can either be relaxed, pleasant, a precursor
to sleep) or boredom, vacuity, dullness). Anyway,

My question was I agree simple (maybe stupid). Most statistical tests
that I know of look for differences in means, or averages (and when
you average across arousal experience you obviously get something like
the Yerkes-Dodson law, that there is an "optimum level" of arousal -
but Reversal Theory would claim that average conceals the underlying
bi-stable dynamic). One can of course play with the mathematics - I
think Clyde Coombs once published an article where he tried to show
that all single peaked preference curves (which are unbiquitous in
Psychology) could be explained as the average of two opposite
tendencies. I could find the refeence in the Psychological Bulletin if
you desire. But my question was really an attempt to try to get away
from the creation of single-peaked average curves and test the sort of
claims that are being made - that these preference curves actually are
the result of a underlying dynamic of discrete but alternating states.
I understand that perhaps I am just being idiotic, or displaying
ignorance. But if I am an idiot or ignorant I would like to discover
why I'm an idiotic or where my ignorance lies.

Lance


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Gary  
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 More options Jul 3, 10:31 pm
Newsgroups: sci.stat.math
From: Gary <LanceG...@gmail.com>
Date: Fri, 3 Jul 2009 05:31:29 -0700 (PDT)
Local: Fri, Jul 3 2009 10:31 pm
Subject: Re: A test for discrete versus continuous?

I think that is the work of Paul Meehl? I found many of his papers to
be extremely insightful. I will look it up.

Lance


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Gary  
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 More options Jul 3, 10:37 pm
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From: Gary <LanceG...@gmail.com>
Date: Fri, 3 Jul 2009 05:37:38 -0700 (PDT)
Local: Fri, Jul 3 2009 10:37 pm
Subject: Re: A test for discrete versus continuous?

Depends on the how fine your measuring instruments are (perhaps with
brain scans and the like they may become much more refined) and it
depends on whether you replicate measurements (because in the sort of
theory I was referring to replications may concela the very thing you
are trying to understand). I think the same kinds of questions that I
was posing have arisen in phsyics and biology - though of course that
doesn't mean that psychologists are not just dumb. But do notice that
Psychology has been around since the 1870s, and that there are more
than 200 000 of them in the USA at the moment, and that statistically
it is highly unlikely that all of them over the entire time period,
are stupid.

Lance


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Gary  
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 More options Jul 3, 10:53 pm
Newsgroups: sci.stat.math
From: Gary <LanceG...@gmail.com>
Date: Fri, 3 Jul 2009 05:53:44 -0700 (PDT)
Local: Fri, Jul 3 2009 10:53 pm
Subject: Re: A test for discrete versus continuous?

This sounds profound to me but I'm not sure that I can apply it to
sort of examples I was offering. In Fulda's account of weakness of
will, he asks you to imagine two cases, where a person X and a person
Y are confined to particular rooms. In one room a person X of very
strong character and high moral principles is confined along with some
object of temptation. Perhaps the temptation is a bribe, or perhaps a
very beautiful woman who is not his wife. Anyway, being of good
character the Person X is capable of resisting temptation so
effectively that he will obly succumb once in a hundred temptations.
But here he is, exposed to the object of temptation and unable to get
away. Now Fulda reasons that in this situation, person X is still very
likely to succumb to the temptation because everytime his mind moves
off whatever he is using to distract his thoughts the temptation will
be there again, and over the course of time he will likely experience
more than a hundred occasions of temptation. In the other room is a
person Y who is of poor character and very weak willed. He will be
able to resist temptation only once in a hundred times. Again his
temptation is there before him. However, in his case, his room has a
button that if pushed, will whisk the temptation away so that it can
no longer be reached or enjoyed. Just that one push will be enough to
save person Y from moral failure. Now Fulda argues that person Y only
needs one moment of strength to save his virture. So he argues person
Y (though very weak willed) will be likely to emerge from the room
unscathed by moral failure, unlike person X (who of course was very
strong willed). One objection raised to Fulda's argument, for what it
is worth, is that the probabilities involved would not be discrete (as
his argument suggests - particular moments of temptation - but would
be continuous, and that therefore the argument does not hold. What do
you think? How can Fulda support his claim (perhaps using pigeons in
Skinner boxes as George Ainslie did, to avoid ethical objections)?
What kind of evidence would count?

Lance


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Gary  
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 More options Jul 3, 10:56 pm
Newsgroups: sci.stat.math
From: Gary <LanceG...@gmail.com>
Date: Fri, 3 Jul 2009 05:56:26 -0700 (PDT)
Local: Fri, Jul 3 2009 10:56 pm
Subject: Re: A test for discrete versus continuous?

Who do you think has no grasp of scientific method? If it is me, OK, I
know I am stupid and ignorant. If it is Paul Meehl I do suggest that
you read some of his papers. He seems to me to be an extremely subtle
thinker.

Cheers

lance


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illywhacker  
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 More options Jul 3, 11:08 pm
Newsgroups: sci.stat.math
From: illywhacker <illywac...@gmail.com>
Date: Fri, 3 Jul 2009 06:08:31 -0700 (PDT)
Local: Fri, Jul 3 2009 11:08 pm
Subject: Re: A test for discrete versus continuous?
On Jul 3, 2:30 pm, Gary <LanceG...@gmail.com> wrote:

No one (least of all me) was suggesting that you are idiotic. Everyone
is ignorant, as Socrates told us. I just find it hard to know what you
are talking about when many of the words you use are so poorly
defined. What is a mental state? Why is introspection relevant? Does a
psycholgical state exist in any meaningful sense (certainly it does
not exist in the way a chair exists)? I am afraid I view this kind of
psychology as akin to fiction, in that it provides metaphors and ways
of talking about ourselves that are useful. This is absolutely not an
insult. It does mean, however, that applying scientific techniques to
it misses the point rather.

Having said that: equilibria (if that is the right way to think of
'mental states' that are in some sense stable in time) are necessarily
(unless there is a continuous symmetry), points in some space of
states, since they are local minima of some potential. Passing from
one to another as a parameter varies is often, although not always) a
discontinuous process. Check out first- and second-order phase
transitions or catastrophe theory.

illywhacker;


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illywhacker  
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 More options Jul 3, 11:24 pm
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From: illywhacker <illywac...@gmail.com>
Date: Fri, 3 Jul 2009 06:24:40 -0700 (PDT)
Local: Fri, Jul 3 2009 11:24 pm
Subject: Re: A test for discrete versus continuous?
On Jul 3, 2:56 pm, Gary <LanceG...@gmail.com> wrote:

See my reply to your earlier post.

illywhacker;


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aruzinsky  
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 More options Jul 4, 12:45 am
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From: aruzinsky <aruzin...@general-cathexis.com>
Date: Fri, 3 Jul 2009 07:45:04 -0700 (PDT)
Local: Sat, Jul 4 2009 12:45 am
Subject: Re: A test for discrete versus continuous?
On Jul 3, 6:53 am, Gary <LanceG...@gmail.com> wrote:

"It is the idea that we experience the content of
our minds and the feelings our body generates in discrete but bi-
stable ways. So when you are relaxing in the evening you might not
mind that nothing much is happening - you will take that as
pleasureable and not seek arousal and not be worried that your goals
are not being achieved."

That sounds like asleep vs. awake which I agree is bistable.
Otherwise, I haven't noticed much bistability.  For example, the
degrees of my hunger, thirst, or pain seems continuous.


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Gary  
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 More options Jul 4, 7:05 am
Newsgroups: sci.stat.math
From: Gary <LanceG...@gmail.com>
Date: Fri, 3 Jul 2009 14:05:36 -0700 (PDT)
Local: Sat, Jul 4 2009 7:05 am
Subject: Re: A test for discrete versus continuous?
On Jul 3, 4:45 pm, aruzinsky <aruzin...@general-cathexis.com> wrote:

Well no one is claiming that every psychological characteristic is
bistable. The original claim was that homeostasis rules in all things
physiological and your examples (not pain) are obviously governed by
homeostatic systems. But that doesn't mean that the work/play
distinction (roughly telic/paratelic) or the flow of air through your
nostrils, or many other things are not better modeled by bistable
systems. Pain is perceptual, and most perceptual systems have neural
coding schemes (which are not continuous) but which are experienced as
continuous. Speech sounds are sometimes claimed to be perceived
categorically (on a spectrometer sound forms are clearly continuous,
but your ear has trouble perceiving sounds between (say) 'b' and 'p').

Lance


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Gary  
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 More options Jul 4, 7:08 am
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From: Gary <LanceG...@gmail.com>
Date: Fri, 3 Jul 2009 14:08:31 -0700 (PDT)
Local: Sat, Jul 4 2009 7:08 am
Subject: Re: A test for discrete versus continuous?
On Jul 3, 3:08 pm, illywhacker <illywac...@gmail.com> wrote:

Thanks for the catastrophe theory reference. The authors of reversal
theory did in fact consider catastrophe theory when developing their
ideas.

As for your first paragraph it seems like I would have to write a book
to answer you. Another time perhaps.

Lance


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illywhacker  
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 More options Jul 4, 4:24 pm
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From: illywhacker <illywac...@gmail.com>
Date: Fri, 3 Jul 2009 23:24:03 -0700 (PDT)
Local: Sat, Jul 4 2009 4:24 pm
Subject: Re: A test for discrete versus continuous?
On Jul 3, 11:08 pm, Gary <LanceG...@gmail.com> wrote:

Catastrophe theory is a limited version of the theory of phase
transitions. I suggest you check that out.

illywhacker;


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sfrthomas  
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 More options Jul 15, 6:49 am
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From: sfrthomas <sfrtho...@yahoo.com>
Date: Tue, 14 Jul 2009 13:49:45 -0700 (PDT)
Local: Wed, Jul 15 2009 6:49 am
Subject: Re: A test for discrete versus continuous?
On Jul 2, 5:46 am, Gary <LanceG...@gmail.com> wrote:

> ((cuts))
> Similarly Fulda
> developed a mathematical model of the pull of temptation and asserts
> that the model works on discrete moments of thought (in other words
> the probabilities of temptation that are being modelled are discrete
> and not continuous).

The domain of the probability (mass) function is discrete. The range,
however, may remain continuous -- at least conceptually. This may seem
a small point, but it goes to the heart of the question later posed...

In my experience it is really hard to devise

> tests for claims of this kind. I wondered whther there are any
> existing statistical tests designed to to test hypotheses of this
> kind, or whether there are procedures and designs suitable for testing
> such claims?

All measurement is ultimately discrete, since there is no measurement
device or reporting procedure that may return as its report a literal
point, precise to an infinite number of decimal places. In a finite
life, nobody has the time either to make such a report, or to wait for
one.

Nevertheless -- and this is the key conceptual point -- it is useful
to conceive of certain attributes -- e.g. height, weight, probability
-- as defining a continuous domain. Measurement reports with respect
to such domain will ultimately define only a cluster of points, e.g.
an interval, either crisp, or more generally fuzzy, within such a
domain.

For example, the 30 cm. ruler on my desk has but 300 markings along
its continuous edge. Therefore, a measurement made with it may be
precise only to within about +/- 1 mm, even if there were no
calibration error, and no systematic error involved in its use.

This may seem irrelevant to the concern expressed, but consider this:
the notion of a discrete psychological state may arise from some
complex of underlying variables, some of which may be inherently
discrete, others of which may be continuous. I am not a psychologist,
and know nothing of reversal theory, but I know something about
statistics and measurement, so please bear with me. Consider the
attribute of race. Clearly it is a discrete, not a continuous
attribute. If we walk down the street we may walk past ten strangers,
and be able to make, to a high degree of accuracy, a determination of
race for each one. (No arguments please, I mean race in the social
sense we all understand.) But if you think about it, we rely for such
determination on a complex of variables -- skin color, hair texture,
width and shape of nose, degree of prognathism, gait, among others --
some of which are conceptually continuous (e.g. skin color, width of
nose, degree of prognathism), others of which we may deem to be
conceptually discrete (e.g. hair texture, although even here we may
allow for *degrees* of curliness). My point is that these underlying
variables define a multi-dimensional space involving continuous and
discrete dimensions, yet we may abstract from this multi-dimensional
space to give an unerring (by and large) description of the race of
someone -- a clearly discrete variable -- we merely pass by on the
street. In effect, we assign a relatively small number of discrete
"racial" markers to point clusters within the afore-mentioned multi-
dimensional space, and thus move from a continuous multi-dimensional
space to a uni-dimensional discrete space.

I suspect something similar is going on with reversal theory. This
however is not the point. The bigger point is that a continuous space
exists only in our imagination -- any child will grasp the *concept*
of a continuum, by contemplating the straight edge of a ruler.
However, actual measurement -- psychometric or otherwise -- must
necessarily be discrete, and involve some finer or coarser amount of
clustering of points that may be assigned to various neighborhoods of
points within a latent or underlying continuous space. We do it for
length measurement with my ruler, and we do it for race "measurement"
when we walk down the street.

The upshot of this, for the question you ask, is that whether you
contemplate a discrete variable or continuous variable, is an act of
imagination that is logically prior to any application of statistical
method. Further, even if by your act of imagination you contemplate a
continuous attribute (eg. the aforementioned ruler on my desk with its
continuous straight edge), measurements made with respect to that
attribute may only ever be discretely many. (The same goes for the
measurement of probability btw, even though it is conceptually clearly
a continuous attribute on the [0,1] interval). And further, as with
"measurement" of race, the discretely many measurements may involve
such coarse clustering that we may be tempted to think of the
attribute as inherently discrete, when on a closer examination we may
find some number of underlying attributes which may themselves be
continuous.

I say all of that to sum up with the following short answer:
statistical hypothesis testing, and indeed statistical inference
procedures more generally, may only come into play *after*
measurements (however coarse) have been taken, and may shed no light
per se on the act of imagination by which one accords to an attribute
the qualities of discreteness or continuity as the case may be.

I hope that is helpful. I have come late to the thread, and I notice
that the discussion seems to have veered off in a direction that may
have left the, very good, question you raised still deserving of
further response.

Kind regards,
S. F. Thomas

P.S. I had to think deeply about this kind of issue in writing my
(1995) _Fuzziness and Probability_. ACG Press.


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Gary  
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 More options Jul 15, 6:50 pm
Newsgroups: sci.stat.math
From: Gary <lanceg...@gmail.com>
Date: Wed, 15 Jul 2009 01:50:58 -0700 (PDT)
Local: Wed, Jul 15 2009 6:50 pm
Subject: Re: A test for discrete versus continuous?
On Jul 14, 10:49 pm, sfrthomas <sfrtho...@yahoo.com> wrote:

Thanks. I will have to think about what you have written.

Lance


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illywhacker  
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 More options Jul 18, 2:15 am
Newsgroups: sci.stat.math
From: illywhacker <illywac...@gmail.com>
Date: Fri, 17 Jul 2009 09:15:34 -0700 (PDT)
Local: Sat, Jul 18 2009 2:15 am
Subject: Re: A test for discrete versus continuous?
On 14 July, 22:49, sfrthomas <sfrtho...@yahoo.com> wrote:

> Nevertheless -- and this is the key conceptual point -- it is useful
> to conceive of certain attributes -- e.g. height, weight, probability
> -- as defining a continuous domain. Measurement reports with respect
> to such domain will ultimately define only a cluster of points, e.g.
> an interval, either crisp, or more generally fuzzy, within such a
> domain.

Probability is not a physical, measurable quantity. It is by
definition real-valued.

> Consider the
> attribute of race. Clearly it is a discrete, not a continuous
> attribute. If we walk down the street we may walk past ten strangers,
> and be able to make, to a high degree of accuracy, a determination of
> race for each one. (No arguments please, I mean race in the social
> sense we all understand.)

Why no arguments? The fact that the majortiy of members of a group may
be classified as you say has nothing to do with whether the attribute
is 'discrete' or not. All classifications are discrete. And, as a
matter of fact, there are plenty of people for whom it is rather hard
to assign a 'race'. People may self-identify, but this is another
question. The very need for self-identification shows that things are
not clear cut.

illywhacker;


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