[Phys-l] Hypotheses (Was:unbiased experiments +- index of refraction)

["John Clement" <clement@hal-pc.org>]

I would say that the majority of physics papers do not follow the
traditional hypothesis first format.  Actually I think it is more often the
case that if there is a hypothesis is in the form of "theory predicts
that..." so they seek to see if the prediction is verified.  The hypothesis
then consists of a prediction based on theory, and not a mechanism for what
you expect.  But then there are experiments such as "... sees a structure in
the spectrum with poor statistics...is it there?"  You don't commit to an
outcome, and merely investigate to see if the effect is there.  This might
actually be more scientific because the experimenter is neutral about the
outcome.

However in some of the sciences the papers follow the hypothesis first
format more closely.  In the science education papers you will see this more
often.  But you do not know if the hypothesis was actually hatched before
the experiment, or was inserted into the paper later.  So for example when
Lawson changes the ordering of the text he hypothesizes that the learning
cycle ordering produces greater learning.  And indeed that did happen.  The
effect as I recall was 20% greater comprehension.  But one could just as
well say that they are investigating the effect of the rearranged text
instead of calling it a hypothesis.  I think the formal hypothesis in
published papers is used much more often in the biological sciences.  But is
the hypothesis real, or just a format used in writing the paper?

The hypothesis testing format is strongly embedded in middle school science
texts.  Often times this type of activity appears at the end of the chapter
under the heading. THINKING...  An experiment is proposed and students are
supposed to generate a little science fair type lab.  Meanwhile Sadler has
shown that very open ended explorations may be helpful to students with high
math skills, but is the kiss of death to students with low math skills.
Looking at most of these little labs I picture the students never really
engaging with the important concepts.  The entire 5 step scientific method
goes back to the time of Newton, and many historians of science have since
debunked it.  Some even claim there is no scientific method, as scientists
follow the same general steps as researchers in other disciplines.

Now making a prediction as to what you might see before a demonstration is
useful pedagogically because Crouch and Mazur have shown that it improves
retention and learning.  This is the basis of the ILDs, but the experiment
has to happen while the prediction or guess is still in short term memory.
That way when it is stored in long term memory, it is modified when the
experiment is discrepant.  But this is hardly a hypothesis.  It is also used
in the McDermott predict, confront, resolve cycle.

One thing one wonders about is what experiments produced no result.  What
interventions were useless?  These are sometimes reported, but not that
often.  The blind alleys are just as interesting, and are useful information
to other researchers.  Ron Thornton nicely reported both the null and
positive results in a talk that he gave a number of years ago.  He expected
that low gaining students would ask fewer questions, but that was not true.
The quality of the question, however, clearly distinguished the low from the
high gainers.  Karplus, according to reports, had a tall stack of activities
that did not work, and a small stack of ones that did.  The ones that failed
are just as interesting as the ones that were successful, but only the
successful ones were published.  The failed ones could have been used as
possible guides to future developers.

A personal story about how failures can be instructive involved my thesis.
The thesis involved doing neutron cross sections on Deuterium.  There was a
researcher in England by the same name doing similar work, but he
fortunately changed course.  Oak Ridge, as I recall, was doing the same
work, but they were using deuterated benzene.  They got their samples, and
then sent one out for analysis.  It cam back OK, so they poured all of the
samples into the chamber and did the experiment.  It had wild peaks which
were totally unexpected.  So they poured the sample out into a glass
container and looked at it.  It had a meniscus.  Well it seemed that one
bottle had water rather than deuterated benzene.  They abandoned the
experiment, fortunately for me.  So hearing about this tends to make one
more careful when making up samples.  Measure twice, cut once.

John M. Clement
Houston, TX

> > Generally inquiry labs do not have the traditional lab report
> > format because there is no hypothesis, just a question "What the heck
> > happens".
>
> This is a good feature, since it follows the common procedure of real
> science more closely (either asking the "What the heck happens"
> question, or following a lead in a hypothesis-based experiment that
> leads off in some direction largely unrelated to the original
> question). I have seen too many elementary science labs that ask the
> students to predict some result about which they know absolutely
> nothing in the beginning. The answers given to this question are then
> turned into a "hypothesis" for the experiment, but the "hypothesis"
> is nothing but a wild guess, based on nothing. Labs based on "what
> happens when . . ." or "what if . . ." or "how can we . . ." -type
> questions are, IMO, much more reasonable approaches.
>
> Of course there are hypothesis testing experiments in the real
> science lab, but I rather think that, if they are not in the
> minority, they are at least not among the most important of those
> done. I think that the capture of science education by the crowd that
> insists that *every* experiment must be one where a stated hypothesis
> is tested have distorted students' views of what science is, and have
> led to some very tortured experimental designs in science fairs and
> other competitions.
>
> Hugh
>
> --
> Hugh Haskell
> mailto:hugh@ieer.org
> mailto:hhaskell@mindspring,.com
>
> So-called "global warming" is just a secret ploy by wacko
> tree-huggers to make America energy independent, clean our air and
> water, improve the fuel efficiency of our vehicles, kick-start
> 21st-century industries, and make our cities safer. Don't let them
> get away with it!!
>
> 					Chip Giller, Founder, Grist.org
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