BTGmoderatorLU wrote:Source: Magoosh
In nine independent trials, what is the probability that Outcome A happens at least once?
1) The probability that Outcome A does not happen even once in any of the nine trials is 0.026.
2) The probability of Outcome A resulting in a single trial is 1/3.
The OA is D
Instead of calculating the probability that Outcome A happens at least once, it's better we calculate the probability that Outcome A does not happen even once; once we get this value, we would deduct it from 1 and get the answer.
Probability that Outcome A happens at least once = 1 - Probability that Outcome A does not happen even once in 9 trials
Let's take each statement one by one.
1) The probability that Outcome A does not happen even once in any of the nine trials is 0.026.
=> Probability that Outcome A happens at least once = 1 - Probability that Outcome A does not happen even once in 9 trials = 1 - 0.026 = A unique value. Sufficient.
2) The probability of Outcome A resulting in a single trial is 1/3.
Probability that Outcome A does not happen in a single trial = 1 - 1/3 = 2/3
Probability that Outcome A does not happen even once in 9 trials = (2/3)^9
Probability that Outcome A happens at least once = 1 - (2/3)^9 = A unique value. Sufficient.
The correct answer:
D
Hope this helps!
-Jay
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