Probability Distribution of X, Y & N(i): Questions & Answers

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The discussion focuses on identifying probability distributions for various scenarios involving random variables X, Y, and N(i). For the first scenario with k urns and n balls, the distribution for X is presumed to be uniform due to insufficient information. The second scenario, involving throwing two dice until a pair of sixes appears, follows a geometric distribution for X. The third scenario regarding the operation times of batteries A, B, and C was initially misunderstood, leading to a correction that it was not a valid problem. Lastly, the distribution for N(i), representing the throw when a specific number appears for the first time, is also geometric.
JohanL
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I have some simple questions about distributions in probability.
what are the distributions for X, Y and N(i) in these cases:

1. You have k urns and n balls. X is the number of balls in one urn.

2. You throw two dices until you get a pair of sixes. X is the number of throws.

3. You have three batteris A,B and C. There durations (? how long they last. I am from sweden) have exponential distributions with DIFFERENT parameters. If you first use A and B in a lamp what is the distribution for X, the time the
lamp works. Then you replace the nonworking battery with battery C. What is the distribution for Y, the time the lamp works after the exchange.

4. You throw one dice over and over again. Let N(i) be the throw when you get i for the first time. What is the distribution for N(i).

Thank you.

I have no problem to do the calculations when i know the distributions. The hard point for me is to figure out the distributions...my book isn't so good.
 
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1. not enough information. you presumably uniformly distributed.

2 is geometric

3. scratch 3, that was wrong.

4. geometric again.
 
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Thx
But what's wrong with 3...its a problem from the book.
 
my answer was wrong, not the question.
 
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