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Re: right or wrong?

On Mon, 12 May 1997, LUDWIK KOWALSKI wrote:

The "formula" quoted in the original post is clearly telling the students
that the purpose of scientific experiment and measurement is to get the
right answer, reinforcing the notion that the content of our discipline is
one of memorizable facts rather than a process for examining the world
around us.

How can I teach, and grade lab reports, if I do not accept the idea that
"the purpose of scientific experiment and measurement is to get the right
answer"? In one setup the right answer may be 9.8 +/- 0.2 while in another
it can be 9.8 +/- 2 (or +/- 0.0002, if you a prospector). The answer does
not have to be quantitative but it is always either right or wrong. That
is why teaching physics is different from teaching artistic subjects, for
example.

I think the point is that in the real world of experimental physics, you
don't know the "right" answer in advance. You may have a theoretically
expected answer, you may have an answer that somebody else measured a few
months ago in another lab... The object is not to find somebody
else's right answer.

When a student measures a value, the so-called "percent error" is not what
tells them how good the value is, and they should not be taught that it
does. What they have is a percent discrepancy. Take your two examples
from above. Two students measure 'g' in a lab. One gets 9.8 +/- 0.2 from
the best line and "max/min" slopes. The other gets 9.8 +/- 2. Both of
them proudly announce a 0 % error based on the formula. However, if we
are to believe the real error analysis they did, one of them did a much
better job on the experiment than the other. In fact, a student who gets
9.6 +/- 0.2 has done better than a student who gets 9.8 +/- 0.6 in spite
of what they may conclude from the "percent error analysis" that the lab
book tells them to do.

|++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++|
| Doug Craigen |
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| If you think Physics is no laughing matter, think again .... |
| http://cyberspc.mb.ca/~dcc/phys/humor.html |
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