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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Why isn't adding the ways to achieve every mutually exclusive outcome giving me the denominator in the birthday problem for four people?
Why isn't adding the ways to achieve every mutually exclusive outcome giving me the denominator in the birthday problem for four people?
$$\binom{4}{2} \cdot 365 \cdot 364 +\binom{4}{3} \cdot 365 \...
user1289955
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Where in the original statement of the birthday problem is the order people of assign matter in the numerator of the probability?
In $\dfrac{365 \choose \#people}{365^{\#people}}$
this counts no repeats for the probability of none assuming Jan, Feb, March is the same thing as Feb, March Jan.
If
We interpret the question as ...
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Birthday Paradox Variant: Probability of getting X days with only one birthday [duplicate]
I don't know whether this question has been asked or not, or if it's on the Wikipedia, and apologies if so but I wanted to know:
Given a group of n people, what is the probability of X people having ...
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Is there a closed-form inverse of the Birthday Problem equation over the interval $1 < k < n + 1$?
The Birthday Problem deals with the probability that, in a set of $k$ randomly-chosen people, at least two will share a birthday. It can be generalized to similar questions of a match with any pair ...
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Expected number of days which are birthdays for k people - confused by linearity intuition
I understand this has been asked before but I still cannot understand the intuition behind it. A lot of the answers I've seen seem to just state that it's due to linearity of expectation and that it ...
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Probability that among $n$ random people, at least two have coinciding or successive birthdays
I found the following riddle:
What is the probability that among $n$ people chosen randomly, at least two of them have their birthdays with at most one day difference.
Note: December 31 and January ...
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Doubts about the Birthday Problem [closed]
I was thinking about the birthday problem, in a slight different version. In the birthday problem, no date is chosen in advance. The variant I'm thinking of is then "same birthday as you", ...
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How do the graphs of the "Birthday Probability" functions work?
The question was to find the probabilities that:
At least two people have the same birthday
Only two people have the same birthday
Nobody has same birthdays
in a room of n people.
I did find the ...
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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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Chance that a group of $n$ people collectively have a missing birthday.
Suppose there is a city with $n$ residents, what is the probability that there is some day in the year at which none of them have their birthday?
In other words, suppose we divide $n$ balls into $k=...
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Ongoing "cost" of generating a number at random until it doesn't collide
There's a company which gives each customer a unique numeric ID (between 10000000-99990000). Every time a new customer record is created, the algorithm generates a random number and checks if the ID ...
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Why can't I use a direct approach in the birthday problem?
In a variation of the birthday problem, we are trying to find the probability that another student in the class shares our birthday. We can use the complement rule to find the probability that a ...
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Need to explain the result of the birthday problem?
I am working with a question of birthday problem, and here is the case I have to solve:
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Clarify the solution for the birthday problem with more than 2 people in a group of n people
I am a newbie with the Statistic and Probability, and I was encountered with the birthday problem. And here is is the question I have to answer:
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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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