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[Phys-L] liars + visualization + Sports Illustrated



It seems to me that physics class ought to teach people how to
take data, and how to make sense of data ... or other folks'
data.

I reckon there is room for improvement in this department.

Data /visualization/ is important. It helps to look at data in
more than one way.

For example, if somebody is foolish enough or dishonest enough to
pick out one ten-year interval from a noisy data set, and tries
to sell you on some policy decision based thereon, you should
insist on seeing *all* the ten-year intervals.

I plotted up some temperature data to show how this works. There
are some intervals of slower-than-average warming, and also some
intervals of faster-than-average warming. The 10-year intervals
are of course noisier than the 20-year intervals.

The fluctuations tell you nothing about what happens next. One
manifestation of this is the infamous "Sports Illustrated Cover
Jinx".

The diagrams and a more-detailed discussion can be found at
https://www.av8n.com/physics/probability-intro.htm#sec-2d-scatter
and
https://www.av8n.com/physics/probability-intro.htm#sec-reversion

Real data has fluctuations. It’s the nature of the beast. If you’ve
only got two or three data points, a large amount of noise can be
fatal ... but if you’ve got hundreds or thousands of data points,
you can tolerate quite a bit of noise, and still reach valid
conclusions, if you analyze things properly.

---------------------------
Pedagogical remarks:

Students shouldn't start with the climate data. Start with
something like tack-tossing data, where the physics is simple.
The physics of the tack is not changing from toss to toss,
and is not mixed up with politically-driven BS.
https://www.av8n.com/physics/tack-tossing.htm

As for the climate data, consider the hypothesis that there
is no "hiatus" but only a fluctuation in the data. Suppose
the suggestion has been made that maybe we ought to look at
*all* the ten-year intervals, to see what's typical and what's
not. For me, it is ridiculously easy to download the data
and use a spreadsheet to scatter-plot the intervals. I know
what the scatter plot ought to look like, and I've done this
sort of thing so many times I can do it in my sleep.

I don't expect undergraduates to come up with this hypothesis on
their own, and I realize there are about ten places where they
could get stuck while trying to construct the scatter plot ...
but you can give them hints. With enough hints any halfway
competent undergrad ought to be able to plot up this data and
understand what it means.

It's not rocket science. The point is to figure out what's a
trend and what's just a fluctuation.