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So I started studying probability and while it seemed all ok I'm having trouble wrapping my head around this one. So the question is: We have 100 balls , 10 black and 90 white. In 50 tries what is the probability of getting 0 to 10 black balls? Now I need to get probability for excels BINOM.DIST function and am having dilemma. Do we need to calculate 1 black divided by total black (10) or getting 10 black out of 100 total? I get 0.1 for both cases and that makes this bit more confusing.

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    $\begingroup$ if this is HW please add the self-study tag $\endgroup$ – Antoine May 22 '16 at 18:26
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    $\begingroup$ Your question is vaguely worded: could you please be more specific? After all, it's obvious that you must get somewhere between 0 and 10 black balls in 50 tries, making the probability 100%. That's so trivial, though, I would guess you really want to compute eleven separate probabilities: the chance of getting exactly zero black balls in 50 "tries," the chance of getting exactly one black ball in 50 "tries," etc. That brings up another ambiguity: what exactly is a "try"? It sounds like it would be observing the color of a single randomly drawn ball and then replacing it. Is this so? $\endgroup$ – whuber May 22 '16 at 22:55
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Draws with replacement

Assuming you mean draws with replacement by tries:

To help you clarify the question: Is the probability in the binomial distribution the probability of a success or is the probability of drawing a particular ball given a success?

Draws without replacement

If you are looking for a distribution and draws without replacement. (ie what is the probability of drawing 0,1,2,3...?) then you should consider:

How many different states/draws there are where you take 50 from 100 balls? How many of the 10 black balls would you draw? How many of the white balls would you draw? How can you combine these into a probability?

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