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Re: [Phys-L] Indicators of quality teaching (Was:MOOC:EdxOffers Mechanics course by Prof.Walter Lewin)

On 06/23/2013 08:10 PM, Richard Tarara wrote:

The 'different curricula' can amount to 'teaching to the test' in
subtle (or overt) ways. The FCI requires a pretty deep understanding
of Newton's Laws although Master's and PhD level physicists mostly
find it trivial. A standard curriculum/book spends a week at best on
this topic. Any curriculum that spends more time and more focus is
teaching _more_ to the test than a more traditional one. The
Thornton test, as I recall, has a lot of graphical analysis built in
(which graph describes the given motion type of question). I would
think that as a pre-test many students would find that KIND of
question unfamiliar and therefore do badly..partly due to there lack
of experience with such. Now if the curriculum in question actually
spends considerable time with this kind of analysis (and I'm not
saying it shouldn't) then post-test gains could be expected to be
high. In both cases the content may be quite different from a
traditional course. OK--students do better so maybe the different
content course is better.....but, my concern is for what is NOT
covered in order to spend the additional time and effort in certain
content areas. [Yes the old breadth versus depth debate, but we do
pass some of these students on to the next course where there might
be expectations of coverage (engineering programs for example).]

Wow, thanks, that is exactly the sort of thoughtful answer I was
hoping for. That clarified my thoughts quite a bit.

I was particularly taken with this sentence:

The FCI requires a pretty deep understanding
of Newton's Laws although Master's and PhD level physicists mostly
find it trivial.

I reckon that's important. I agree with it about 98 percent. I
would however like to make the point that "deep" is not the same
as arcane. Deep principles are sometimes relatively easy to learn,
even in the introductory course ... deep principles such as conservation
of momentum. Arcane would be bad, but deep is not necessarily bad
or difficult.

Let's discuss this in the context of some actual data. On the FCI,
6 of the 30 questions are what I would call third-law questions.
(I'm talking about questions 4, 15, 16, 17, 25, and 28.)
a) The professional physicist looks at one of these six questions,
sees a few easy ways to get the wrong answer, and then sees an
easy way to get the right answer. The same correct technique
works for all six questions. See below for details. The whole
process is over in less time than it takes to tell about it.
b) All available data indicates that students very commonly get
some of these questions right and some of them wrong. I see only
one way to interpret this: The students must not be recognizing
the questions as third-law questions. I see them as thinly-disguised
applications of the third law, but evidently students cannot so easily
see through the disguise.

I conjecture that /part/ of this dichotomy can be explained as follows:
a) The expert can look at the problem from five different directions.
In one of those directions, the disguise fails, and the applicability
of the third law is obvious.
b) The student can look at the problem in only one way. They learned
one approach and stopped there. Some of this is inevitable, due to
lack of time; students are by definition short on experience. OTOH
part of it is due to defective strategy that allowed them to think
that one approach would be enough. /This is a fixable problem./

If I'm even partly right about this, the all-too-common lousy scores
(and lousy gains) on the FCI don't mean we should put more emphasis on
the concepts that appear on that test; it means we should teach more
about the strategy of reasoning. That is to say, I reckon the "deep"
physics concepts required for the FCI are pretty easy to learn. The
challenges lie elsewhere. Some of the questions reward looking at the
problem in five different ways ... which is a strategy that students
were not born knowing. It can be learned and can be taught, but it's
not easy.

I'm trying to get people to appreciate the unity and grandeur and
simplicity of physics. The nifty thing about physics is that there
are a handful of simple principles -- concepts, if you will -- that
can be *combined* in very powerful ways. OTOH if you don't know how
to combine the principles, physics is like OSB (oriented strand board)
without glue: it's just a loose pile of wood chips, with no useful
structure. It's like reinforced concrete without the Portland cement:
It's just a loose pile of stuff, with no way to give it useful structure.

This is why teaching to the test is utterly demented, if the test
revolves around FCI -- by which I mean Force Concepts in Isolation.
The isolation is a problem. Teaching to such a test is self-defeating,
because students are not stupid: They can tell that /isolated/ physics
factoids are useless.

If you ask me, the first good "indicator of quality teaching" is whether
the students have a good attitude toward learning and thinking.

The cornerstone of critical thinking is "check your work". The next
step beyond that involves checking the other guy's work. Multiple-guess
tests, especially simple ones like the FCI, carry this to a ridiculous
extreme, because you don't actually have to figure anything out; you
just need to /check/ the hypothetical answers and rule out the ones
that don't pass the checks.

This requires applying /multiple/ checks to each hypothesis.
-- Does it uphold Galileo's principle of relativity?
-- Does it uphold conservation of energy?
-- Does it uphold conservation of momentum?
-- et cetera.

The list is not very long. This may sound almost like equation-hunting,
but it is different in a fundamental way:
-- Equation hunting means finding the magical equation that solves the
problem, and stopping there.
++ Checking the fundamental principles means looking for a principle
that applies, and *not* stopping there, because there may well be
other principles that also apply.

Another fundamental difference:
-- The total number of equations in the world is very large, and it
is not practical to search them all.
++ The total number of fundamental principles is very small.

=============

Another "indicator of quality teaching" is the students' ability to
carry out multi-step /chains/ of reasoning.

At this point we have an irony, an inconsistency. Most people think
FCI is /supposed/ to measure Force Concepts in Isolation. It is
/supposed/ to be insensitive to reasoning skills ... and to a first
approximation that is true. However, it is not entirely true. If
a student gets the right answer to all six third-law questions, the
usual practice is to interpret that as mastery of the action-reaction
idea, but I'm not convinced. It could mean that the student used
reasoning skills to answer the problems using an indirect approach,
as detailed below.

So, if you want to measure "quality teaching" as I understand the
term, you cannot begin to do it using FCI gain.
-- In reinforced concrete, the gravel is important, but it is pretty
much useless without the Portland cement to bind it together.
-- In physics, force concepts are important, but they are pretty
much useless without multi-step chains of reasoning to bind them
together.

To the extent that FCI measures what it is supposed to measure, it
is a terrible way to measure "quality teaching". And to the extent
that it doesn't measure what it is supposed to measure, that's not
really an improvement. It is sensitive enough to reasoning skills
to muddy the water, but not sensitive enough to provide a usable
measurement of reasoning skills.

Measuring FCI gain is an extreme form of looking under the lamp-post.
It's easy to do ... but most of what you are looking for is elsewhere.

=========================================

Returning to the six third-law questions. Do these really require
a "deep" understanding of physics? Technically, yes ... but I'm not
sure that's the right question, because deep does not necessarily
mean difficult or sophisticated or out of place in the introductory
course. There's a ridiculously simple trick that allows you to answer
all six third-law questions in about a millisecond.

-- The test is supposedly about forces.
-- The questions ask about forces.
-- The third law is typically formulated in terms of forces ...
equal and opposite reaction and all that.
++ You do not, however, need to do things that way. Just because
somebody is tempting you to think in terms of forces doesn't mean
you must succumb to the temptation.
++ The third law is tantamount to conservation of momentum.

Does conservation of momentum require a "deep" understanding of physics?
I suppose so, because in all of physics there is hardly anything deeper
than conservation of momentum. On the other hand, this concept is not
one more iota more difficult than the concept of action and reaction.
It is connected to other conservation principles. It is connected to
other things we know about momentum. Therefore talking about it is
another opportunity to stress the unity and grandeur and simplicity
of physics.

The FCI will always be hard if you try to keep track of the forces.
Smart people who do this sort of thing for a living can't keep track
of the forces. They keep track of the momentum instead.

The interesting thing here is the idea that sometimes the direct
approach doesn't pay. It reminds me of a not-very-bright person
on one side of the fence, with food on the other side of the fence.
He's banging his head against the fence, with no good result ...
but the fence is short and open at both ends, and all he had to do
is walk around, taking a slightly indirect approach.

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My point is simple: It isn't necessary or even helpful to put more emphasis
on isolated physics /concepts/. The momentum concept is not arcane or tricky.
The conservation concept is not arcane or tricky. The only halfway tricky
thing here is the reasoning: The problem comes to you in terms of forces,
but you solve it in terms of momentum.

It seems to me that "conceptual physics" has become a euphemism for "bonehead
physics" because the so-called conceptual physics courses focus on the factoids
in isolation, to the neglect of the reasoning that binds things together and
makes them useful.

This is a fixable problem! Teach the reasoning skills!
http://www.av8n.com/physics/thinking.htm