ISI 2015 PEA Answer Key - Discuss

[kk]

yes answer of question 27 will be c..as its given without replacement...

[kk]

how to do ques 2 of PEB??

[L]

P(w2) does not mean probability of getting second ball white given that first is white.
You need find the probability of getting second ball white irrespective of the colour of first ball.

[kk]

yes that is fine.but the number of balls will decrease..it will be w+b-1 after the first draw as there will be no replacement..so the total probability will be P(w2) =P(w2|w1)+ P(w2|b1)
the answre will not be a...and can u help me in solving ques 2 of peb

[deepti]

If anyone is taking coaching from amit goyal then please contact him n ask when he'll be able to upload the answers. Also plz hlp with subjective part of 2015

On May 1, 2015 10:38 AM, "kk [via Discussion forum]" <[hidden email]> wrote:

yes that is fine.but the number of balls will decrease..it will be w+b-1 after the first draw as there will be no replacement..so the total probability will be P(w2) =P(w2|w1)+ P(w2|b1)
the answre will not be a...and can u help me in solving ques 2 of peb

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[L]

Your Law of total probability function is wrong.

P(w2) =P(w2|w1)+ P(w2|b1) ------WRONG

P(w2) =P(w2|w1) P(w1)+ P(w2|b1)P(b1)    -----CORRECT

If you are still not getting the answer, then, you need to revise probability.


For 2nd ques of PEB, 2015, go through this link http://discussion-forum.2150183.n2.nabble.com/ISI-2015-sample-question-Stumped-td7595937.html.

The solution has been removed, but you will still get  some idea. This question is very malleable, almost everybody has different answers, and we don't know what is the correct one.
May be Amit sir can give the correct one.

[deepti]

Please find the solutions of subjective type questions.. n ask him wt shud be the ans. Of probability question

On May 1, 2015 7:09 PM, "L [via Discussion forum]" <[hidden email]> wrote:

You Law of total probability function is wrong.

P(w2) =P(w2|w1)+ P(w2|b1) ------WRONG

P(w2) =P(w2|w1) P(w1)+ P(w2|b1)P(b1)    -----CORRECT

If you are still not getting the answer, then, you need to revise probability.


For 2nd ques of PEB, 2015, go through this link http://discussion-forum.2150183.n2.nabble.com/ISI-2015-sample-question-Stumped-td7595937.html.

The solution has been removed, but you will still get  some idea. This question is very malleable, almost everybody has different answers, and we don't know what is the correct one.
May be Amit sir can give the correct one.

---

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NAML

[kk]

yes you are correct..I made a mistake..thank u so much

[dhruv]

For que 29, I was getting A, as E(X.Y) = E(X).E(Y) = 0, therefore, they are independent and r = 0.

Please, verify and correct my mistake if any.