Question

Probability question

Answer 1

Let's say I have 3 blue balls in a bag of 10 balls.
I will take out 15 balls, with reposition. I need to find the probability that 5 of them are blue.

Would doing
\[\left(\begin{matrix}15 \\ 5\end{matrix}\right)\(\frac{ 3 }{ 10 })^{5}\frac{ 7 }{ 10 }^{10}\]

Answer 2

Would that be the correct start?

Answer 3

how is it even possible that you take out 15 balls in a bag that has only 10 balls?

Answer 4

How can you take 15 balls out of a bag of 10 balls?

Answer 5

It is reposition, you take one out, you see the color, you put inside the bag again

Answer 6

ah..ok

Answer 7

\[P(5\ blue\ out\ of\ 15)=\left(\begin{matrix}15 \\ 5\end{matrix}\right)(\frac{3}{10})^{5}(\frac{7}{10})^{10}\]

Answer 8

And if I need the probability that as a max there are 5 blue balls? I need to do all the expansion up to 5?

Answer 9

Yes, you need to find the binomial probabilities for 0, 1, 2, 3, 4 and 5 blue balls. Then add these 6 values of probability to find the probability of no more than 5 blue balls.

Answer 10

Perfect, thanks :D

Answer 11

You're welcome :)