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When a coin is flipped, the probability of getting heads is

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When a coin is flipped, the probability of getting heads is [#permalink] New post 13 Mar 2019, 12:10
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Question Stats:

66% (03:19) correct 33% (01:02) wrong based on 30 sessions
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.
[Reveal] Spoiler: OA

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Re: When a coin is flipped, the probability of getting heads is [#permalink] New post 16 Mar 2019, 06:23
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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
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Re: When a coin is flipped, the probability of getting heads is   [#permalink] 16 Mar 2019, 06:23
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When a coin is flipped, the probability of getting heads is

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