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Aviral1995
08 Jan 2020, 08:33
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VeritasKarishma thankyou for your prompt reply...but i think i am missing something.could you please explain me the whole second scenario - why do we need to multiply by 1/5 and why can't we directly take 5/6 * 1/4 into consideration...please help!
08 Jan 2020, 22:32
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Hi Aviral1995
5/6 is the probability that the die shows any number other than 4
1/4 is the probability that he tells a lie
Now, if he tells a lie he can say anything from any 5 number apart from the actual number
the probability that he chooses to quote 4 is /15
hence the total probability that he doesn't get a 4, but he tells a lie and reports it 4 will be
5/6 *1/4* 1/5
Hope it is clear now.
5/6 is the probability that the die shows any number other than 4
1/4 is the probability that he tells a lie
Now, if he tells a lie he can say anything from any 5 number apart from the actual number
the probability that he chooses to quote 4 is /15
hence the total probability that he doesn't get a 4, but he tells a lie and reports it 4 will be
5/6 *1/4* 1/5
Hope it is clear now.
Aviral1995
01 Feb 2020, 08:56
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I do not know if my approach is wrong but I managed to get the same result. Correct me if I'm wrong. I already understood all the previous posts 
Prob( being4 AND not_lying) = Prob(4) + Prob (Not_Lying) - Prob (intersection) Not really sure about the intersection's part.
Ok, let's compute the calculus. Prob(being4 AND not_lying) = 1/6 + 1/4 - 1/4*1/6 = 10/24 - 1/24 = 9/24 = 3/8
As I highlighted I'm not really sure about the rigurosity of my personal approach on the intersection part.
Prob( being4 AND not_lying) = Prob(4) + Prob (Not_Lying) - Prob (intersection) Not really sure about the intersection's part.
Ok, let's compute the calculus. Prob(being4 AND not_lying) = 1/6 + 1/4 - 1/4*1/6 = 10/24 - 1/24 = 9/24 = 3/8
As I highlighted I'm not really sure about the rigurosity of my personal approach on the intersection part.
