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Probability distribution pin code guessing

by Max.Planck
Tags: code, distribution, guessing, probability
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Max.Planck
#1
Mar7-12, 04:57 PM
P: 127
1. The problem statement, all variables and given/known data
What is the distribution of stochastic variable X = "the number of attempts needed to find the correct last digit of a pin code"


2. Relevant equations



3. The attempt at a solution
I thought it was like this:
P(X=1) = 1/10
P(X=2) = 9/10*1/9
P(X=3) = 9/10*8/9*1/7
...
...
P(X=10) = 9/10*8/9*7/8*6/7*5/6*4/5*3/4*2/3*1/2*1

Thank you!
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Ray Vickson
#2
Mar7-12, 05:06 PM
Sci Advisor
HW Helper
Thanks
P: 4,939
Quote Quote by Max.Planck View Post
1. The problem statement, all variables and given/known data
What is the distribution of stochastic variable X = "the number of attempts needed to find the correct last digit of a pin code"


2. Relevant equations



3. The attempt at a solution
I thought it was like this:
P(X=1) = 1/10
P(X=2) = 9/10*1/9
P(X=3) = 9/10*8/9*1/7
...
...
P(X=10) = 9/10*8/9*7/8*6/7*5/6*4/5*3/4*2/3*1/2*1

Thank you!
Looks good.

RGV
Max.Planck
#3
Mar7-12, 06:20 PM
P: 127
Quote Quote by Ray Vickson View Post
Looks good.

RGV
Thanks. Is it possible to capture P(X=x) in a formula?


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