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by maihuna » Tue Mar 15, 2011 12:20 pm
In the period between 1975 and 1985, the population of each of
the Â…ve major cities in country C increased by at least 10,000
people. If the standard deviation of the populations in 1975
was 35,000 people, what was the standard deviation of the
populations in 1985?
(1) The total increase in population of the Â…ve cities from
1975 to 1985 was 220,000 people.
(2) Each of the Â…ve cities increased in population by 12% in
the period between 1975 and 1985.
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Source: — Data Sufficiency |
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by force5 » Tue Mar 15, 2011 1:44 pm
MY Take is B , what's the OA?
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by Night reader » Tue Mar 15, 2011 3:12 pm
hi maihuna, an excellent question testing SD concept which follows:

New Mean or New SD = Old Mean or old SD * (1+% increase/decrease)

as we see st(1) is Not Sufficient, we are given only total increase
st(2) is also Sufficient, we are given the percentage increase and the question can be answered SD in 1985 = SD in 1975 * 1.12

IOM B
maihuna wrote:In the period between 1975 and 1985, the population of each of
the Â…ve major cities in country C increased by at least 10,000
people. If the standard deviation of the populations in 1975
was 35,000 people, what was the standard deviation of the
populations in 1985?
(1) The total increase in population of the Â…ve cities from
1975 to 1985 was 220,000 people.
(2) Each of the Â…ve cities increased in population by 12% in
the period between 1975 and 1985.
Last edited by Night reader on Thu Mar 17, 2011 5:13 am, edited 1 time in total.
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by force5 » Wed Mar 16, 2011 11:12 am
Maihuna can you post the OA please.......
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by luiscarlos59 » Wed Mar 16, 2011 9:47 pm
I go with B
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by srcc25anu » Thu Mar 17, 2011 1:16 am
i think it should be B
since each of the 5 cities' population is growing by 12%, new sd = old sd * 1.12 or 35000*1.12
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by Target2009 » Thu Mar 17, 2011 11:09 am
one more B
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by maihuna » Fri Mar 18, 2011 6:35 am
OA Is B
force5 wrote:Maihuna can you post the OA please.......
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