Latest IBM Aptitude Question SOLUTION: An experiment succeeds twice as often as it fails. What is the probability that in the next 5 trials there will be four successes?

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An experiment succeeds twice as often as it fails. What is the probability that in the next 5 trials there will be four successes?

Asked In IBM (12 years ago)

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Nisarg Raval  (11 years ago)

An experiment succeeds twice as often as it fails.

i.e. the probability of its success is 2/3 and the probability of its failure is 1/3.

In the next 5 trials the experiment needs to succeed in 4 out of the 5 trials.

4 out of the 5 trials in which it succeeds could be selected in 5C4 ways = 5 ways.

And as 4 of them are successes, they have a probability of 2/3 and the one that is a failure will have a probability of 1/3.

Hence, the required probability = 5*((2/3)^4)*(1/3)

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vinodkumar  (12 years ago)

according to bernoullis equation p(X=r)=ncr*p^r*q^n-r;
p=probability of success,q=probability of fail=1-p;
so here p=2q=2(1-p)=2-2p;
p=2/3;q=1/3; 4 success probability=p(4)=5c4*(2/3)^4*(1/3)^1=5*16*1/3^5=80/243

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