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Topic: spinning pennies
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Bob Hayden

Posts: 2,384
Registered: 12/6/04
spinning pennies
Posted: Nov 14, 1996 10:24 PM
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I have heard a number of stories about how mint and year affect the
percentage of heads for spun pennies. Does anyone have any hard data
on this? I have not spun pennies in some years, but when I did I
gathered enough data to make me question the stories I had heard.

One thing I learned from coin activities is that modern youth --
especially modern male youth -- don't carry any coins with them. So,
I provided coins haphazardly chosen from the accumulation on my
nightstand. I then collected the coins and the results from each
student. There was a LOT more variability than I would expect if
p=0.50 for all pennies. So, I packaged the pennies in numbered
envelopes and tried them with one or two other classes. Generally,
they replicated the results of the first. Pennies that gave unusually
large numbers of heads with one class did so with another. (One class
never knew the results of previous classes until AFTER they spun the
pennies and reported THEIR results.) However, another penny of the
same date and mint might give consistent results around p=0.5 or even
p<0.5. So, I wondered if the things I had heard were based on large
numbers of pennies matched for year and mint, or if someone just
happened to have a 1953 penny that acted weird but was simply
ASSUMING that to be a property of all 1953 pennies rather than that

This seems like an activity of interest to high school teachers and
students, who may have more time for activities, so perhaps people
would like to pool their results into a National Investigation of Spun
Penny Orientation (NISPO). (I only had students spin pennies in
classes that met in a room with flat desks -- an unusual event around

| | Robert W. Hayden
| | Department of Mathematics
/ | Plymouth State College MSC#29
| | Plymouth, New Hampshire 03264 USA
| * | Rural Route 1, Box 10
/ | Ashland, NH 03217-9702
| ) (603) 968-9914 (home)
fax (603) 535-2943 (work)

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