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What is the standard deviation of the values of the 20 coins in a

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What is the standard deviation of the values of the 20 coins in a  [#permalink]

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New post 20 Jun 2016, 11:09
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83% (00:19) correct 17% (00:20) wrong based on 214 sessions

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What is the standard deviation of the values of the 20 coins in a certain jar ?

1. The average (arithmetic mean ) value of the coins in the jar is 25 cents .

2. All 20 coins in the jar have the same value .

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Re: What is the standard deviation of the values of the 20 coins in a  [#permalink]

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New post 21 Jun 2016, 07:19
B.

2)same value means SD=0.

for 1)each value of coin is not given(not Suff)
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Re: What is the standard deviation of the values of the 20 coins in a  [#permalink]

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New post 21 Jun 2016, 10:57
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Skywalker18 wrote:
What is the standard deviation of the values of the 20 coins in a certain jar ?

1. The average (arithmetic mean ) value of the coins in the jar is 25 cents .

2. All 20 coins in the jar have the same value .



1. The average (arithmetic mean ) value of the coins in the jar is 25 cents . We don't know other values to find out standard deviation. Not Sufficient.

2. All 20 coins in the jar have the same value . All the values are same means SD is 0. Sufficient

B is the answer
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Re: What is the standard deviation of the values of the 20 coins in a  [#permalink]

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New post 01 Jul 2016, 20:32
This is tagged as a 600 - 700 level question, but it seems much easier than that. Sub 600 at best.
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Re: What is the standard deviation of the values of the 20 coins in a  [#permalink]

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New post 02 Jul 2016, 04:55
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Re: What is the standard deviation of the values of the 20 coins in a  [#permalink]

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New post 19 Jan 2018, 09:00
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Skywalker18 wrote:
What is the standard deviation of the values of the 20 coins in a certain jar ?

1. The average (arithmetic mean ) value of the coins in the jar is 25 cents .

2. All 20 coins in the jar have the same value .



Target question: What is the standard deviation of the values of the 20 coins in a certain jar ?

Statement 1: The average (arithmetic mean ) value of the coins in the jar is 25 cents .
There are several cases that satisfy statement 1. Here are two:
Case a: All 20 coins are quarters (each is worth $0.25). This meets this condition that the average value is 25 cents. In this case, the standard deviation EQUALS 0
Case b: The 20 coins are NOT all quarters. In this case, the standard deviation does NOT equal 0
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: All 20 coins in the jar have the same value
The means the standard deviation EQUALS 0
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: B

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Re: What is the standard deviation of the values of the 20 coins in a &nbs [#permalink] 19 Jan 2018, 09:00
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