What is the probability of throwing the same number exactly 3 times?

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Homework Help Overview

The discussion revolves around calculating the probability of rolling the same number on a die exactly three times out of five rolls. The subject area is probability theory, specifically focusing on combinatorial methods and the binomial distribution.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • The original poster attempts various techniques, including combinatorial counting and the binomial distribution, to determine the probability. They express confusion about the correct approach and the number of valid sequences.

Discussion Status

Participants are actively exploring different methods to solve the problem. Some guidance has been offered regarding the structure of sequences and the application of the binomial distribution, but there is no explicit consensus on the correct solution yet.

Contextual Notes

The original poster notes discrepancies in their calculations and questions the validity of their approaches, indicating a need for clarification on the correct interpretation of the problem.

Dell
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we throw a dice 5 times,
what is the probability of throwing the same number exactly 3 times?

i tried using all kinds of techuniques but can't seem to get this,

if A is a given number and X is any other number

A* A* A* X* X
6* 1* 1* 5* 5 =150

150/6^5=0.0192901

but that doesn't take into account any other options, for example A*X*A*X*A, X*A*A*X*A ...

so then i thought since i can either roll a given number or not, and the possibility that i will is 1/6

X~B(5,1/6)

P(X=3)=5C3*(1/6)^3*(5/6)^2=0.03215

the correct answer is 0.19,- which makes me think my 1st attempt was correct and there are 10 options, but how do i find these options and also, why is the binomial incorrect??
 
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If you take one possible sequence as you've done, giving AAAXX with A being the number of choice, what is the probability of achieving this sequence? How many other possibilities are there to mix up the order of the above sequence, such as AAXAX etc. ? And finally, how many possible numbers for A are there?

The same result can be achieved by the binomial distribution method.
 


thanks i got it, i found the probability of a cerain number 3 times, i need to multiply by 6
 


You got to love those silly mistakes :biggrin:
 

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