From: blohman@coastside.net
Date: Mon, 26 Apr 1999 19:34:42 -0700
To: pinhole@exploratorium.edu
Subject: probability
The answer to the probability question depends on how you ask it. There
certainly is a 50% chance that 2 children will be of opposite sexes
because there are 2 ways that this can happen, BG and GB. There also is
a 50% probability that they will be of the same sex, BB or GG. However
if you meet a woman and have to guess the sex of her sibling it is not a
question of the probability of 2 events. The events are independent,
her sex does not affect the sex of her sibling (theoretically of course,
let's not get into the biology, etc). So she has a 50% chance of having
a male sibling, no matter which side, older or younger. Students should
have had enough probability in their math classes to handle this
question fairly competently. Of course they may not want to admit that
they know something from another class!!