All Questions
Tagged with birthday permutations
15
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Understanding the generalized "Birthday Problem" formula [duplicate]
While practicing frequently asked probability questions during interviews, I came across the classical "Birthday problem". While I understand some of the reasoning explained on wikipedia, ...
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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 ...
user1289970
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Birthday Problem: Finding a Probability Function of an Event
Problem: Ignoring leap days, the days of the year can be numbered $1$ to $365$. Assume that birthdays
are equally likely to fall on any day of the year. Consider a group of $n$ people, of which
you ...
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Find the probability that at least two people out of $k$ people will have the same birthday
The Birthday problem. Find the probability that at least two people out of $(k=5)$ people will have the same birthday.
The usual approach would be to use $$p=1-\frac{P_{365,5}}{365^5}$$
However, I ...
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Probability of at least 3 people sharing a common birthday
What is the probability that 3 or more people share a common birthday, in a group of 160 people?
Approach:
We have:
$P(X\geq 3)= 1-[P(X=0)+P(X=2)]$.
(where $X\geq i$ means at least $i$ people share a ...
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Birthday problem but with $2^{128}$ different days in the year [duplicate]
I am trying to calculate how many randomly generated ids I need to produce for there to be a 1% probability I get a duplicate id.
There are $2^{128}$ possible ids.
I understand this is just the ...
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Birthday problem: solving with permutations vs combinations
I have a problem with an exercise:
If k people are at a party, what is the probability that at least two of them have the same birthday? Suppose that there are n=365 days in a year and all days are ...
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3
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Birthday paradox question
I am solving the question:
How large must a class be to make the probability of finding two people with the same birthday at least 50%?
The first solution I came up with is rather simple. It's based ...
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What is the probability of 1st January being the birthday of two persons among 500?
$\mathbf{Question:}$ What is the probability of $1$st January being the birthday of $two$ people when chosen (two persons are picked randomly) among $500$ people? ($365$ days in a Year).
$\mathbf{...
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What is the probability that in a company of $500$ people, only two persons will have birthdays on New Year’s Day?
What is the probability that in a company of 500 people, only two persons will have birthdays on New Year’s Day?
I feel the answer is
=$\frac{1}{365}\cdot\frac{1}{365}\cdot\frac{364}{365}\cdot\frac{...
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Birthday probability of $k$ people and $n$ days a year such that at least $2$ people have the same bday
A certain planet has n days in one year. What is the probability that among $k$ people on that planet there are (at least) two who share their birthday?
My answer to this practice question is:
There ...
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Birthday Paradox 2 pairs
I have followed the various birthday paradox posts. Can someone please assist with the logic for finding the probability of two pairs of people with the same birthday in a group of $23$. If $n=23$ ...
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Distinct birthdays problem. Verification of solution.
Question Consider $n$ people who are attending a party. We assume that every person has an equal probability of being born on every day of the year, independent of everyone else. Assuming that nobody ...
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Group of $r$ people at least three people have the same birthday?
What is the probability that in a randomly chosen group of $r$ people at least three people have the same birthday?
$\displaystyle 1- \frac{365\cdot364 \cdots(365-r+1)}{365^r}$
$\displaystyle \frac{...
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At least two people have the same birthday
If there are 85 students in a statistics class and we assume that there are 365 days in a year, what is the probability that at least two students in the class have the same birthday?
I tried solving ...
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