Questions tagged [birthday]
Birthday problems typically look at probabilities and expectations of a random group of individuals sharing birthdays and how this changes as the number of people increase. They often assume that individuals' birthdays are independently uniformly distributed across 365 days but similar problems can use other numbers or assumptions. They can be generalised to wider occupancy and collision problems.
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Variation of Birthday problem with n people and exactly t pairs sharing the same birthday
The problem statement is simple: Let there be a group of n people. What is the probability that exactly t pairs will share the same birthday?
All my attempts to solve this problem came down to the ...
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How many people must be in a room until it is at least a $50\%$ chance that two will have the same amount of change?
Book problem: If the amount of change in a pocket is assumed to be uniformly distributed from $0$ to $99$ cents, how many people must be in a room until it is at least a $50\%$ chance that two will ...
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how many persons need to be in one room , so AT LEAST 3 people have the same Birth MONTH?
how many persons need to be in one room , so AT LEAST 3 people have the same Birth MONTH ?
Another Answer i suggest : (correct me if i'm wrong) there should be 15 People at least , because if there's ...
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Generalized Birthday Problem? Combinatorics
I am having a difficult time understanding how to think about and analyze the following problem:
(I have done research, but I am not sure how to phrase my enquiries and my research seems to be almost ...
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Birthday problem: Poisson vs binomial random variable
From this post, the birthday problem involving more than 2 people can be approximated using a Poisson random variable. But I am wondering whether a binomial random variable can be used here. I imagine ...
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Birthday problem for people knowing each other
Suppose a large chat room for a country, what is the probability that two people know each other in real-life?
We have:
n: The number of people in the chat room
d: The number of persons the average ...
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Birthday problem variant
There are $n$ people present in a room. Assume that people’s
birthdays are equally likely to be on any day of the year.
What is the probability that at least one of them celebrates their birthday on ...
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Variation on Birthday Paradox Problem
So, I have read the birthday paradox problem, and now I came across below question:
Assuming the following: there are no leap years, all years have $n = 365$ days and that people’s birthdays
are ...
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Generalized birthday paradox, expected number of birthday days
Suppose we have m objects and we draw one uniformly n times with replacement. Some objects will be drawn at least once, some never. What is the expected value of the number of objects that are drawn, ...
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Same Birthday Probability
Two people are said to have the same birthday if they were born in the same month and on the same day of the month (the year of birth is not relevant). If there is are 40 people in a room, compute ...
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Same birthday question: 2 different variants have same answer?
How many people must there be before the chances that someone
has the same birthday as you do is at least 0.5? How many people must there be
before the chances that at least two people have a birthday ...
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Expected number of collsions in hashing
Suppose we use a hash function h to hash n keys into m slots. Assuming simple uniform hashing, what is the expected number of collisions? (CLRS, 3rd edition, problem 11.2-1)
My solution is as follows:
...
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What is the probability that $n$ persons have birthdays all within one half year?
I'm wondering what the probability is that $n$ persons have birthdays all within 1/2 year.
For instance, two persons always have birthdays within 1/2 year, as the maximal distance between two days is ...
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Estimate of peoples sharing the same first name, last name and date of birth over a population
I am aware of the birthday paradox (more than 50% likeliness of two people sharing the same day of birth). My question is somehow related to this, but with more variables (and unknowns).
Given a total ...
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Formula for the probability of two people with the same name in a group.
I'm looking to figure out a formula that can help me calculate the probability that two people in a group share the same full name. Specifically, my question is: In a group of $X$ people (ranging ...
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