[xquery-talk] Izzit Bcos I is functional?

Ihe Onwuka ihe.onwuka at gmail.com
Thu Jun 18 21:55:56 PDT 2015

```On Thu, Jun 18, 2015 at 6:13 PM, Ihe Onwuka <ihe.onwuka at gmail.com> wrote:

>
>> Pick a Box A.
>
> Sampling is without replaceent.
> Chance of 1st ball being black = 3/6 = 1/2
> Chance of 2nd ball being black = 2/5.
>
> Chance of both being blank = 1//2 * 2/5 = 1/5.
>
> BUT there are 2 ways for Box A to have 2 black balls
>
> a). Box B could have zero black and Box C 1 black  or
> b) Box C could have zero black and Box B 1 white.
> So multiply by 2
>
> Se P (Box A has 2 black balls) = 1/5 * 2 = 2/5.
>
> BUT there is only a one in 3  chance of selecting Box A
>
> Final answer = 2/5 * 1/3 = 2/15
>
> I settle for partial credit.
>
>
Good thing I only aimed for partial credit as I got it wrong and I guess it
is because I over-elaborated.

If you've seen 1 black ball there are 5 other possible balls to  choose
from only 2 of which are black.

No need to multiply the probability of picking that box (1/3) because that
is given information.

So by sampling without replacement the probability is 2/5.