Carcass wrote:
When a coin is flipped, the probability of getting heads is 0.5, and the probability of getting tails is 0.5 A coin is flipped 5 times.
Quantity A |
Quantity B |
Probability of getting exactly 2 heads |
Probability of getting exactly 3 heads |
A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.
Since P(heads) = P(tails), we know that:
P(0 HEADS in 5 flips) = P(0 TAILS in 5 flips)
P(1 HEAD in 5 flips) = P(1 TAIL in 5 flips)
P(2 HEADS in 5 flips) = P(2 TAILS in 5 flips)
P(3 HEADS in 5 flips) = P(3 TAILS in 5 flips)
P(4 HEADS in 5 flips) = P(4 TAILS in 5 flips)
P(5 HEADS in 5 flips) = P(5 TAILS in 5 flips)
Now notice that getting 2 TAILS in 5 flips is exactly the same as getting 3 HEADS in 5 flips
[if 2 flips are tails, then the other 3 flips must be heads] So, we can write: P(2 HEADS in 5 flips) = P(2 TAILS in 5 flips) = = P(3 HEADS in 5 flips)
Answer: C
Cheers,
Brent
_________________
Brent Hanneson – Creator of greenlighttestprep.com
If you enjoy my solutions, you'll like my GRE prep course.
Sign up for GRE Question of the Day emails