Probability 4 Question 6

6. Let H1,H2,,Hn be mutually exclusive events with P(Hi)>0,i=1,2,,n. Let E be any other event with 0<P(E)<1.

Statement I P(Hi/E)>P(E/Hi)P(Hi) for i=1,2,,n Statement II i=1nP(Hi)=1

(2007, 3M)

Passage Based Problems

Passage I

Let n1 and n2 be the number of red and black balls, respectively in box I. Let n3 and n4 be the number of red and black balls, respectively in box II.

(2015 Adv.)

Show Answer

Answer:

Correct Answer: 6. (d)

Solution:

  1. Statement I If P(HiE)=0 for some i, then

PHiE=PEHi=0

If P(HiE)0,i=1,2,,n, then

PHiE=P(HiE)P(Hi)×P(Hi)P(E)=PEHi×P(Hi)P(E)>PEHiP(Hi)[0<P(E)<1]

Hence, Statement I may not always be true.

Statement II Clearly, H1H2Hn=S

[sample space]

P(H1)+P(H2)++P(Hn)=1

Hence, Statement II is ture.

Passage I



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