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Read the two articles on the question of whether vitamins
are bad for you.

The Brodie article states that ``Smokers who took 20
milligrams of beta carotene each day developed 18
percent more lung cancers than those who were given
vitamin E or a dummy pill.'' What does this mean? What
additional information would you need to decide if this
difference is significant?

In the original article (New England Journal of
Medicine, 14 April 1994) you will find that during the
study there were 876 newly diagnosed cases of lung
cancer with 474 among those who were given beta
carotene and 402 among those who were not. The study
was designed in such a way that there was essentially a
50% chance that each subject would be given
beta carotene.
If beta carotene has no effect then it might be
reasonable to assume that the number of deaths among those who
took beta carotene can be compared to the number of
heads in tossing a coin 876 times. What is the
approximate probability of getting 474 or more heads
when a fair coin is tossed 876 times? Is this
consistent with the claim that the increase in
incidence of lung cancer for those taking beta carotene
is significant at the 95% level?

On the basis of this study, Laurie has quit taking
beta carotene. Was this a wise decision?
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laurie.snell@chance.dartmouth.edu