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George Weigt 2006-09-29 12:14:03 -07:00
parent 589a27f732
commit 834aad1e10
1 changed files with 2 additions and 2 deletions

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118.tex
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@ -1,7 +1,7 @@
An urn contains 50 tickets, each with a different number from
1 to 50. If 7 tickets are drawn at random without replacement,
what is the probability that the median of these seven numbers
20?
is 20?
\bigskip
Possible ways of selecting 7 tickets:
@ -53,7 +53,7 @@ to be exactly 20.
Another way of looking at it is the $1/50$ factor is already
in the denominator, ${}_{50}C_7$.
Putting something in the numerator increases the probability.
So in a way the ${}_1C_1$ in the numerator lowers the
So in a way, the ${}_1C_1$ in the numerator lowers the
probability because it is a small number.
Anything else would increase the overall probability.