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CHANCE News 2.10
(16 May to 1 June,1993)

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Prepared by Laurie Snell

Please send suggestions for  articles or format to
dart.chance@dartmouth.edu

Previous issues of this chance news and other materials for
a chance course are on the chance gopher.  Just point your
gopher to chance.dartmouth.edu

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I shall never believe that God plays dice with the world.

Albert Einstein
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ARTICLES ABSTRACTED

1.  Formula projects limits seen on human existence.
2.  Exam ruling derails foreign doctor's dream.
3.  Simple test effective in reducing colon cancer deaths.
4.  Colon cancer screening.
6.  The art of turning the tables.
7.  Studies show Vitamin E may reduce heart disease.
8.  Gender bias charged in National Merit Scholarship Test.
9.  Sex differences in performance on the mathematics section.
10.  Little benefit seen in prostate surgery.
11.  NRC report on DNA typing.

<<<========<<

>>>>>==========>>
Here is a contribution from Peter Doyle.

Formula projects limits seen on human existence.
The New York Times, 1 June 1993, Sec. C Page 1.
Macolm W. Browne

J. Richard Gott, Princeton astrophysicist, has written an article
in the current issue of  Nature explaining how to obtain 95%
anything you wish.  The idea is that we find ourselves at a
randomly chosen point of the lifetime of whatever it is, and
thus with probability .95 we are somewhere between 1/40
and 39/40 finished.

Say, for example, we estimate that the human race has been
around for about 200,000 years. If we're only 1/40 of the
way through the lifetime  of the human race, then we have
39 times 200,000  years or about 8 million years left to go.
If  we're at the other end of the 95% confidence  interval, that
is 39/40 of the way through, then  we have only 1/39 times
200,000 years or about  5000 years to go.

Having developed this beautiful rule of thumb,  Gott goes on
to demonstrate, by example, the dangers of taking this kind
of thing too seriously.  He concludes that the space program,
now 32 years old, will (with 95% confidence) end before
another 1200 years are up, surely too short a time for us to
colonize the galaxy and thus escape the 8,000,000 year
deadline derived above.  Fortunately for the human race,
Gott's  whole theory is only about a year old, and thus can
be expected to last somewhere between another 39 years
and another 9 days.  Thus it will most likely die long before
it has a chance to doom the space program, and thereby the
whole human race.
<<<========<<

>>>>>==========>>
Exam ruling derails foreign doctor's dream.
Los Angeles Times, 1 June 1993, A3.
Tony Perry

Luis Garcia-Higgins is a naturalized U.S. citizen who is licensed
as a doctor in Mexico and had thought that, after a number of
unsucessful tries, he had finally passed the Foreign Medical
Graduate Examination taken in San Diego last January.

However, after taking the test he received a letter saying that
a statistical analysis had "revealed a strong relation of joint
wrong answers between you and one or more examinees,
which suggests that the examination may not be a valid
measure of your knowledge".  Actually, the strong relations
was with five people who took the test in New York, one in
Philadelphia and one in  New Orleans.  In all 109 people got
such a letter after the January test.  The letter to Grarcia said
that the "approximate probability" that he arrived at the
answers innocently was "less than one in a billion".

Garcia received the usual offer to take another test but has
decided to fight the case with the help of Professor Peter Irons,
a professor of political science at UC San Diego.  In addition, an
attorney in Rhode Island, Bernard Fergeson,  is considering a
class-action lawsuit on behalf  of medical graduates who have
had their test scores invalidated.  Commission attorney Hubbard
has said that he is confident that their  statistical methods will
withstand professional  review.  Of course, the Commission will
be  careful to say that they have not accused  Garcia of cheating
and so the statistical issue may never get challenged in court
but if it does it will be interesting to follow this case. The article
quotes (not very accurately)  J. Laurie Snell "one of the nation's
leading authorities in probability statistics" (whatever that is).

We used this last article for discussion in our  last CHANCE class.
We decided this time to have the students come up with
questions which they  would then answer in groups. Here are
the  questions they proposed:

Is Garcia being accused of cheating?

Is Garcia a cheater?

Could it be that some questions are harder than  others, so
that people will tend to get the same  questions wrong?

Could the language barrier have been a problem?

Should Garcia volunteer to take the test again?

Would you want this guy to be your doctor?

Shouldn't we be more concerned about matching right

Should there be a limit on the number of times you can
take the test?

Why wasn't the test cancelled?

The questions led to a lively discussion.
<<<========<<

>>>>>==========>>
Report calls simple test effective in reducing colon
cancer deaths.
The New York Times, 13 May, 1993, Section A, Page 1.
Jane E. Brody

After the last chance news, Nathaniel Beck  commented: You
missed the NY Times piece on  using fecal-occult (didn't know
medicine had a  sense of humor!) blood test to detect colon
cancer. Nice discussion on the continuation of  the story inside
on a simple cost-benefit  analysis (though my own cost-benefit
analysis on the numbers presented shows that cost per life
saved is quite reasonable by American standards).
<<<========<<

>>>>>==========>>
Colon cancer screening; contradictory results puzzle researchers.
Washington Post, 25 May, 1993, Page Z9.
Sandra G. Boodman

Researchers at the Mayo Clinic recently  published in the
Journal of American Medical  Association a study that
concluded that simple and widely used stool tests were
ineffective in detecting colon cancer.  The study reported in
the previous article reached as very different  conclusion.
presents the views of  experts on where we are with this
problem (confused).
<<<========<<

>>>>>==========>>
Science, 21 May, 1993.
Editorial by Daniel E. Koshland, Jr

Science has recently published issues on special  topics, such
as women in science, and have  invited reader response and
published a summary  of responses saying, for example, that
76% of  the respondents felt one way about a subject.

Science also received an avalanche of letters  from
statisticians who were concerned with the  use of the word
poll or survey for such a non  scientific  process.  When
Science pointed out  that they were in fact interested in
hearing  from those who felt most strongly enough about
the issues to write and had made no claim to be doing a
accurate poll.

The statisticians responded by saying that  Science was such
a prestigious journal that they  were still worried that people
might think that  this was an o.k. way to do a serious poll.
Apparently, the statisticians involved accepted  the editor's
proposal that this kind of study be   called an "Oyvey" survey.
It is remarked that this change resulted from on Oyvey of
statisticians.
<<<========<<

>>>>>==========>>
The art of turning the tables.
The Times, 20 May 1993, features.
Tom Rhodes

A review of the book THE MONEY SPINNERS, How  Professional
Gamblers beat the Casinos at their  own Game, By Jacque Black,
author's name but that the author has had a great deal of
experience gambling in London casinos.  The book  provides
accounts of some of the famous  characters in gambling such
as Edward Thorpe and a complete account of the history of the
casino  from the Palais Royal in Paris to Las Vegas and Atlantic
City.  The appendices which constitute  about a third of the
book offer guides to games and how to beat the system.
More later after I  have read the book if I find it interesting.
<<<========<<

>>>>>==========>>
Studies show Vitamin E may reduce heart disease.
Los Angeles Times, 20 May, 1993
Sheryl Stolberg

The current issue of the New England Journal of  Medicine
reports two studies, one with men and  one with women that
show that men and women who  took daily Vitamin E
supplements of at least 100  international units had a 40%
lower risk of  heart disease than those that did not.

A possible explanation is that cholesterol must  undergo
oxidation to get inside the cells that  line the walls of blood
vessels and Vitamin E  helps prevent this oxidation.

The studies were based on the Nurses's Health  Study and
the Health Professionals Follow-Up  Study that rely on the
eating  habits.

Authors of the studies recommend waiting until  more
definitive clinical trials are carried out  and until there is
assurance that their are no  long term risks in taking such
large doses of  Vitamin E.  Others point out that this is more
caution that is often advised for a drug which  has much
more potential for harmful side  effects.
<<<========<<

>>>>>==========>>
Gender bias charged in National Merit Scholarship Test.
Los Angeles Times, 26 May, 1993, A1
Elizabeth Shogren

The organization FairTest reports that only  about 35% of the
National Merit Scholarship  winners are girls despite the fact
that studies  suggest that girls do better than boys in grades
in high school and college.  The choice of  semifinalists for the
National Merit Scholarship is based entirely on the  results of
the Preliminary Scholastic Aptitude Test.  The  article refers
to the article below that  documents the fact that women do
less well than men on SAT exams.
<<<========<<

>>>>>==========>>
Sex differences in Performance on the  mathematics section
of the Scholastic Aptitude Test:  A bi-directional validity study.
Harvard Educational Review, Fall 1992.
Howard Wainer and Linda S. Steinberg.

This study by Educational Testing Service  researchers reviews
the literature concerning  the difference between men and
women on the  mathematics SAT tests and reports on their
own  study.  They compare SAT-M scores for men and  women
with the same SAT-M scores. They  show that women
consistently do about thirty  points lower on these tests.
Since women do as  well as men in college this raises questions
and competitive scholarship  programs.  They discuss some
possible solutions  ranging from giving women extra points to
doing  nothing.  The authors favor continuing to try to
understand what is going on.
<<<========<<

>>>>>==========>>
Little benefit seen in prostate surgery
Study finds six fold increase in rate of cancer
operation since 1984 .
Washington Post, 26 May, 1993, A1.
David Brown

An account of an two articles in the current  Journal of the
American Medical Association  related to treatments for
prostate cancer.  One  study considers possible treatments and
suggests that watchful waiting is often  preferred to removing
the prostate through  surgery, or radiation treatment when
prostate  cancer is identified in its early stages.  The  authors
use utility theory methods (indeed even  Markov chain models)
to compare the benefits of  various possible treatments.

The second study finds that the rate of the  performing prostate
surgery has increased 600  percent from 1984 to 1990.  Wide
geographical  variations are found for performing the surgery.
West coast men have the operation almost four  times as often
as those in New England.  A member  of the prostate research
group is quoted in the  New York Times as saying "The take-
home message is that we don't know what w'ere doing, but
we're doing a lot of it'.  The authors suggest  that there is very
little real evidence that surgery is effective and suggest that
if  surgical procedures had to be tested and   approved by the
standards required for drugs  that much of the prostate
surgery being done  would not be permitted with the present
information on the success of the surgery.
<<<========<<

>>>>>==========>>
NRC report on DNA typing.
Science, 21 May, 1993
Letters from B. Devlin, Neil Risch and  Ranajit Chakraborty

Daniel L.Hartl and Richard C.Lewontin wrote a  letter to
Science 23 April (p 473) concerning  the Devlin and Risch
critique (Policy Form, 5  Feb.,p 748) of the National Research
report on  DNA typing.  These letters are in reply to this letter.
The whole collections gives a good view  of the current
controversy over the "multiplication rule" and other questions
relating to the determination of the probability  for a match
in DNA fingerprinting.
<<<========<<

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CHANCE News 2.10
(16 May to 1 June,1993)

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!