Saturday, September 08, 2007

1/ Anastasia, Brenda and Cornelia toss a fair coin 15, 16, and 17 times respectively. Which one is least likely to have tossed more heads than tails?
2/ The same, except the coins are tossed 18, 19, and 20 times respectively?


Blogger steven said...

1/ Brenda.
2/ Anastasia.

A person who tosses an odd number of throws has a 50/50 chance of tossing fewer tails than heads, and vice-versa.

But a person tossing an even number of throws has a possibility that they may throw an equal number of heads and tails. This probability decreases with the number of throws (e.g. with two throws, the probability of tossing an equal number is 1/2; with four throws, it's less, and so on).

So the person tossing the lowest number of even throws has the highest probability of getting equal heads and tails, and therefore the lowest probability of getting more heads than tails.

September 28, 2007 at 3:58 AM  

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