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Kara attends a university where students study for an average (arithme

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Bunuel
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Kara attends a university where students study for an average (arithme [#permalink] New post   16 Aug 2016, 06:13
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E

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72% (00:59) correct 28% (00:51) wrong based on 57 sessions
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Kara attends a university where students study for an average (arithmetic mean) of 13.4 hours per week. How many hours per week does Kara study?

(1) The standard deviation of study time at Kara’s school is 2.8.
(2) Kara’s study time is one standard deviation away from the mean.
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E
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Re: Kara attends a university where students study for an average (arithme [#permalink] New post   16 Aug 2016, 06:41
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Kara attends a university where students study for an average (arithmetic mean) of 13.4 hours per week. How many hours per week does Kara study?

(1) The standard deviation of study time at Kara’s school is 2.8.
(2) Kara’s study time is one standard deviation away from the mean.


Consider 1) Gives the SD, which along with AM of the school is not helpful to find Kara's study time . Eliminate A and D
Consider 2) We know only Mean and nothing else , so no use of this alone. Eliminate B

Consider 1) and 2), AM is 13.4 and SD is 2.8 and Kara is one SD away, which means, it can either be 13.4 + 2.8 or 13.4 - 2.8. Not conclusive.
So answer is E
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Re: Kara attends a university where students study for an average (arithme [#permalink] New post   16 Aug 2016, 08:57
(1) The standard deviation of study time at Kara’s school is 2.8. - not suff
(2) Kara’s study time is one standard deviation away from the mean. - not suff

(1) + (2) together 13.4+ 2.8 or 13.4 - 2.8 = 2 different values.
Together not sufficient

Hence E
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Kara attends a university where students study for an average (arithme [#permalink] New post   16 Aug 2016, 20:26
Bunuel wrote:
Kara attends a university where students study for an average (arithmetic mean) of 13.4 hours per week. How many hours per week does Kara study?

(1) The standard deviation of study time at Kara’s school is 2.8.
(2) Kara’s study time is one standard deviation away from the mean.




1. Whole AM=13.4, whole SD=2.8, no way to figure out kara's study hours so, .not suff A, D out
2. Whole AM=13.4, kara's study time 1 sd away from mean. we do not know the value of sd so, not suff B out

1 and 2 combined. AM= 13.4, Sd.=2.8, kara's study per week= 1 sd away from mean= either 13.4+2.8 or 13.4-2.8. Either way. Hence
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Kara attends a university where students study for an average (arithme [#permalink]
16 Aug 2016, 20:26
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Bunuel
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