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Geometric Distribution?

  • Thread starter rclakmal
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Geometric Distribution???

Geometric Distribution: In an experiment, a die is rolled repeatedly until all six faces have finally shown.?
What is the probability that it only takes six rolls for this event to occur? ANSWER = 0.0007716

What is the expected waiting time for this event to occur? ANSWER = 35 rolls

Thanks a lot for any help.
 

Answers and Replies

  • #2
tiny-tim
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Geometric Distribution: In an experiment, a die is rolled repeatedly until all six faces have finally shown.?
What is the probability that it only takes six rolls for this event to occur? ANSWER = 0.0007716

What is the expected waiting time for this event to occur? ANSWER = 35 rolls

Thanks a lot for any help.
Show us what you've tried, and where you're stuck, and then we'll know how to help! :smile:
 
  • #3
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yr sure ...i know that geometric distribution has the probability of (p)*(1-p)^(x-1) where the first success happens in x trials .

then i thought that ,
number to come in first trial is =(1/6)*(5/6)^(1-1)=1/6
number coming in the second trial =(1/6)*(5/6)^(2-1)=1/6*(5/6)
like wise

probability will be =sigma(x goes 1 to 6 )[(1/6)(5/6)^(x-1)]....but seems that i got the argument wrong.and can u please help me on this and if u can guide me for a site where some easy examples on this it will be really helpful.
 
  • #4
tiny-tim
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yr sure ...i know that geometric distribution has the probability of (p)*(1-p)^(x-1) where the first success happens in x trials .
That formula is really for where you're interested in a fixed result each time (for example, how many 4s are there?) …

Hint: here, you need the 2nd to be different from the 1st, the 3rd to be different from both of them, and so on :wink:

(btw, how did you get on with that other thread?)
 
  • #5
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yr then it should be 1*(5/6)*(4/6)*(3/6)*(2/6)*(1*6) is that so each time u have to remove one number ..........so it should be like this no .....but im not getting the answer., may be the answer is wrong ?or is it right .did u check it ??????anyway thanks for ur helping hands


(what is other thread?i didnt get it ....!)
 
  • #6
tiny-tim
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yr then it should be 1*(5/6)*(4/6)*(3/6)*(2/6)*(1*6) is that so each time u have to remove one number ..........so it should be like this no .....but im not getting the answer., may be the answer is wrong
Yes, that's what I get.

The answer given, 0.0007716, is 1/64 … I don't know how they get that. :frown:

(i meant https://www.physicsforums.com/showthread.php?t=311671)
 

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