How many people are needed to have a 50\% chance of at least two colliding birthdays?

23 people
Due to probability, sometimes an event is more likely to occur than we believe it to. In this case, if you survey a random group of just 23 people there is actually about a 50–50 chance that two of them will have the same birthday. This is known as the birthday paradox.

How many people has to be in a room so you can be sure that there is at least one who has the same birthday as you?

23 people. In a room of just 23 people there’s a 50-50 chance of at least two people having the same birthday. In a room of 75 there’s a 99.9\% chance of at least two people matching. Put down the calculator and pitchfork, I don’t speak heresy. The birthday paradox is strange, counter-intuitive, and completely true.

What is the probability in a room with 20 persons that any two of the persons have the same birthday?

0.411
If there are 366 or more people, but only 365 possible birthdays disregarding leap year, then two or more of them must share a birthday….Probability of Shared Birthdays. or, How to Win Money in Bar Bets.

Probability in a group of n people that 2 or more have the same birthday
20	0.411
22	0.476
23	0.507

How many people share a birthday in a room?

The goal is to compute P(A), the probability that at least two people in the room have the same birthday. However, it is simpler to calculate P(A′), the probability that no two people in the room have the same birthday….Calculating the probability.

n	p(n)
60	99.4\%
70	99.9\%
75	99.97\%
100	99.99997\%

How many people in a room would have a different birthday?

It depends what you mean by probable. Presuming that you mean better than a 50\% chance then the answer is 23 people and the reasoning (ignoging leap years) goes :- Start with one person in a room. Add a second person and the probability that he has a different birthday is 364/365.

What are the chances of two people having the same birthday?

In a room of just 23 people there’s a 50-50 chance of at least two people having the same birthday. In a room of 75 there’s a 99.9\% chance of at least two people matching. Put down the calculator and pitchfork, I don’t speak heresy. The birthday paradox is strange, counter-intuitive, and completely true.

What is the probability of having 3 birthdays in a row?

If a third person joins them, the probability that this new person has a different birthday from those two (i.e., the probability that all three will have different birthdays) is (364/365) x (363/365), about .992.

What is the probability that Betty has a different birthday to Frank?

We then choose another person, Betty. The probability that Betty has a different birthday to Frank is 364/365, as there are 364 days in the year that Frank was not born on. We then grab another person – Shazza – and bring her over to the side.