Probability that seems easy but not

  • Context: Undergrad 
  • Thread starter Thread starter tomz
  • Start date Start date
  • Tags Tags
    Probability
Click For Summary

Discussion Overview

The discussion revolves around calculating the probability that at least one of 25 people is born in each month of the year. Participants explore various methods and approaches to solve this probability problem, including considerations of overlapping probabilities and the application of specific mathematical principles.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant poses the initial question about the likelihood of at least one birthday in each month, expressing confusion over potential methods.
  • Another suggests starting with the probability that none of the 25 people was born in January, indicating a possible pathway to the solution.
  • A participant expresses concern about overlapping probabilities when considering months without birthdays, mentioning their own method of using 11^25.
  • It is noted that the inclusion-exclusion principle could be applied to address the overlapping probabilities.
  • Alternative methods such as Markov matrices and exponential generating functions are mentioned, though one participant admits to not understanding these concepts.
  • A reference to the Coupon Collector's Problem is made, suggesting a related mathematical framework for the discussion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on a specific solution method, and multiple approaches are discussed without resolution. Confusion and uncertainty about the application of different mathematical principles persist.

Contextual Notes

Participants express limitations in understanding certain mathematical concepts and methods, which may affect their ability to engage with the problem fully. The discussion reflects varying levels of familiarity with probability theory.

Who May Find This Useful

This discussion may be useful for individuals interested in probability theory, particularly those exploring birthday problems or similar combinatorial challenges.

tomz
Messages
35
Reaction score
0
Hi, here is the question

if there are 25 people, what is the likelihood that at least one of them is born in each month of the year?


not any formula I can think of, sorry

I have tried everymethod, consider number of month that not contain birthdays, consider allocate the extra 13 people to 12 months. But none of these works. And I am now really confuse.

Any help would be very generous!
Thank you!
 
Physics news on Phys.org
Start by answering the question, "what is the probability that none of the 25 people was born in January".

Then think how to use that (and similar probabilities that are easy to find) to answer the original question.
 
THanks for your reply
But I am still confused, because by considering none in Janurary, it also include the situation none in Feburary, none in march...etc.. (the method I use is just 11^25...) So there is repetitions...

May you enlight me a bit more?
 
tomz said:
THanks for your reply
But I am still confused, because by considering none in Janurary, it also include the situation none in Feburary, none in march...etc.. (the method I use is just 11^25...) So there is repetitions...

May you enlight me a bit more?

You're on the right track - since the probabilities overlap, the inclusion-exclusion principle could be applied.

There's a few other ways to do it (markov matrices, exponential generating functions) but this is probably the most intuitive.
 
Thanks for your reply and the courage you give me!
But I can virtually understand none of the things that you said..
I will try to learn them now!

Thank you very much!
 
thank you so much.
Thats something similar..

I will try this method
 

Similar threads

  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
147
Views
11K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 1 ·
Replies
1
Views
1K
Replies
8
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
6
Views
5K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K