Out of a group of 23 randomly selected people, what is the probability that atleast two were born on the same day?
2007-01-24 04:26:11 · 5 answers · asked by viv_1612 1 in Science & Mathematics ➔ Physics
The prob is 0.507, a very anti-intuitive answer.
P[at least 2 were born on the same day] = 1 - P[nobody born on the same day].
Imagine a bag has 23 balls and the possible value on each ball is 1 to 365.
The sample space (the denominator) is 365 ^ 23 possible outcomes.
The numerator is 365 x (365-1) x (365-2) x ....x (365-22)
In order that all 23 balls do not repeat the same value, the first ball 365 numbers, the 2nd ball can only have 364 numbers in order not to repeat the first ball. And the third ball 363-2.......and 23rd ball has 365-22 ways left in order not to repeat the previous 22 balls.
If you master this, you are on your way to do good in prob class.
Yes. Ignore the leap year.
2007-01-25 12:57:02 · answer #1 · answered by e_kueh 2 · 0⤊ 0⤋
The way to go about it is to calculate the odds that no two were born the same day.
For two people, the odds are 364/365 (ignoring leap year, which adds a whole new level of confusion).
For the third, the odds that he doesn't share a b-day with the other 2 are 363/365. So the total is 363*364 / 365^2
For n people, the probability will be
364*363*...*366-n / 365^n
Then take the complement (1- that) of that to get your answer.
2007-01-24 12:31:35 · answer #2 · answered by Anonymous · 1⤊ 0⤋
P=23/(365*365)
2007-01-24 12:51:41 · answer #3 · answered by JAMES 4 · 0⤊ 1⤋
Extreme.
2007-01-24 12:30:59 · answer #4 · answered by Anonymous · 0⤊ 1⤋
look probability is same thing as heridity...very simple.here is a short movie about probability animated. http://www.brainpop.com/math/dataanalysisandprobability/basicprobability/
2007-01-24 12:32:53 · answer #5 · answered by tonima 4 · 0⤊ 1⤋