- Thread starter Daddii
- Start date
- Tags probability replacement selection

I want a formula that does not use any math notation beyond standard algebra.

Example answer (not correct) (x!*y!)/(x*y)!

I will use the formula to compute the answer.

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I have a bag with 389 black balls, and 2236 white balls. If I randomly draw pairs out of the bag, what number of black/white pairs will I get? What number of black/black pairs will I get? What number of white/white pairs will I get?

In seven replies I have not seen even one math formula. What is with that? What I am looking for is a formula, that I expect will contain fewer characters than your last post does. The formula cannot possibly be modified by anything I have tried, and someone who knows the formula does not need to know what I have tried in order to be able to post it. I have tried looking for examples on the web. Going to a dozen web sites. If you search the way I do you will find a plethora of problem sets from university courses, but no solutions. I might be searching with bad search terms. If you search and find it, then send me your search string. I am a 60 year old man with a doctorate in biophysics. I just want the formula.

We have great probability people here, so we can wait to see if they chime in. Dason was just indirectly referring to posting ettique, of having poster clarify what they have tried. This clears up students just trying to get answers and us telling people to try approaches they have already tried.

I believe you just take x/x+y times y/x+y

Dason was just indirectly referring to posting ettique, of having poster clarify what they have tried.

So the answer in the form of Binomial pmf will be like

\( \binom {2} {1} \left(\frac {x} {x + y}\right)^1 \left(\frac {y} {x + y}\right)^{2-1} \)

As mentioned above, it will be much better to let you think why you have an answer like this before we directly provide it. And actually the rationale behind is not that difficult.