Re: Thomas' Fuzziness and Probability

From: Andrzej Pownuk (pownuk@zeus.polsl.gliwice.pl)
Date: Thu Aug 23 2001 - 07:37:29 MET DST

• Next message: Andrzej Pownuk: "Re: Thomas' Fuzziness and Probability"

What is the probability that Pi is equal to 3?
This is the next example of non-probabilistic error.

> >Probability theory is related
> >with the question
> >"how often something happened".
> >When in each experiment we get the same results,
> >then this problem is not related with theory of probability.
> >We know the answers with probability one.
>
> This is confusing probability with limiting relative
> frequency. One NEVER has this situation, and in any
> case, limits tell one nothing for finite samples.

Unfortunately, I have to agree.
Finite number of samples isn't a good criterion.

> One cannot "repeat" an experiment; the situation is
> always different. So probability has to be looked
> at otherwise. The only reasonable approach I have
> seen is that it exists, and the properties are as
> described. The assumptions one makes, such as
> independence, similarity of moments, etc., are far
> more precise than any observations can yield.
>
> >When I see that knowledge
> >of my students is related with probability,
> >(For the same question I got
> >different response.)
> >then I doubt about their knowledge.
>
> This happens all the time.

Students use different words
in order to described the same fact.
We can see when different answers
are equivalent.

What is the probability that John
know the definition of kinetic energy?

We can check this fact using two or three questions.
If John know don't know the answer then
we can ask him many times,
but with the same result.
John knows or doesn't know.
We know that with probability 1.
THERE IS NOTHING RANDOM
in this situation.
John can't invent definition
of the kinetic energy in the classroom.
(without additional source of information.)

What is the probability that the food is fresh?

I don't know haw to measure this fact,
but the word "fresh" is connected with amount of bacteria
and influence of chemical reactions.
Both factors aren't random in concrete situation.

What is the probability that the glass of water is full?

The word "full" is connected with the following number
m=(volume of water)/(volume of the glass)
This is not random variable in concrete situation.

What is the probability that structure is damage?

This is very difficult question which is connect
with the number of microcrack and many another factors.
The damage of the structure can be measured using different method
but the damage of the structure is not random.
(see for example Engineering Failure Analysis,
Engineering Fracture Mechanics,
International Journal of Fracture)

There is nothing random in the in the height of John.

Andrzej Pownuk

---------------------------------------------
MSc. Andrzej Pownuk
Chair of Theoretical Mechanics
Silesian University of Technology
E-mail: pownuk@zeus.polsl.gliwice.pl
URL: http://zeus.polsl.gliwice.pl/~pownuk
---------------------------------------------

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