# Complement of “at least two people share the same birthday”?

If the opposite of “at least” is “at most”, why is the complement of “at least two people share the same birthday” equal to “no one shares the same birthday” and not “at most two people share the same birthday?” Hi, welcome to Philosophy SE.

Contents

## What is the probability at least 2 people share the same birthday?

The birthday paradox, also known as the birthday problem, states that in a random group of 23 people, there is about a 50 percent chance that two people have the same birthday.

## What is the probability that in a group of 2 people both have same birthday?

now both may have same birthday on one of the 365 days, so P(both have the same b’day) =365/365×365=1/365.

## What is the probability that at least two out of n students have the same birthday in a leap year where all the days are equally likely?

The chance that THEY have the same birthday is 1/365.

## How many people do you need to guarantee two people have the same birthday?

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.

## What is the probability that there are at least two people with the same birthday in a class of 40 students?

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
30 0.706
40 0.891
50 0.970

## What is the probability that in a class of 35 students at least two have the same birthday?

Therefore, we have to calculate the possibility that no two people will have the same birthday, exactly one person will have the same birthday and exactly two people will have the same birthday. Therefore, there is a 83.34% chance that at least two people have the same birthday.

## How do you calculate the probability of the same birthday?

However, it is simpler to calculate P(A′), the probability that no two people in the room have the same birthday. Then, because A and A′ are the only two possibilities and are also mutually exclusive, P(A) = 1 − P(A′).

Calculating the probability.

n p(n)
10 11.7%
20 41.1%
23 50.7%
30 70.6%

## How do you find the probability of at least 2?

We're going to take a look at probability of at least two is one minus the sum of zero.

## How do you solve the birthday paradox?

Start small calculate the odds that just one pair of people have different birthdays. One day in the year will be person as birthday.

## What do you call someone that shares the same birthday?

birthday twins” (born on the same day & same month) “birthdate twins” (born on the same day & same month & same year) “time twins” (born on the same day & same month & same year)

## Are birthdays equally distributed?

In reality, birthdays are not uniformly distributed. The answer is that the probability of a match onlly becomes larger for any deviation from the uniform distribution. This result can be proved rigorously but involves more mathematics.

## What is the probability of 3 people not sharing the same birthday?

The first person has no one to pair with, so the probability of no same birthday is 1 (100%). The second person will not match with the first person with probability 364/365. The third person will not match with the first two with probability 363/356.

## What is the rarest birthday?

This Is the Least Common Birthday in the U.S. (No, It’s Not Leap Day)

• February 29.
• July 5.
• May 26.
• December 31.
• April 13.
• December 23.
• April 1.
• November 28.

## What is the rarest month to be born in?

According to the CDC, February is the least common birth month.

## Is April 13 a common birthday?

Happy birthday to you, and you, and many more. It’s not uncommon to share a birthday with someone you know.

How common of a birth date is each day in the calendar year?

Birth Date Popularity Average Births
4/13 351st 10,389
4/14 307th 10,812
4/15 278th 10,883
4/16 260th 10,909

## Is it true that nobody was born on December 6 2006?

That’s 2843 famous people (and counting) and none of them born on December 6th. The 6th has been the lone holdout for a couple of years now.

## What’s the most popular birthday?

Sept. 9

Birth data shows that Sept. 9 is the most common birthday in the U.S., and September is the busiest month for births overall. There have been several reported data sets that offer a picture of which days and months are the most common for births.

## Is April a rare birthday month?

Also meaning that December is the least common birth month, with January and February sharing a similarly low birth rate. But what does that tell us? Well for one, March, April and May are the least popular months to get it on, according to this study.

## Are April born beautiful?

The April born people always wear a dazzling smile. This is one of the main reasons for their good-looking personality. They are quite intimidating when it comes to appealing for looks. The opposite person should be careful from their tempting looks.

## What month are intelligent babies?

Those born in September are, apparently, the smartest out of the entire year. According to Marie Claire, a study published in the National Bureau of Economic Research found that there’s a clear correlation between the month during which you were born and how smart you are.