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Find the standard deviation of tenmember set Y. (1) the set [#permalink]
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12 Jul 2004, 00:53
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Find the standard deviation of tenmember set Y.
(1) the set is an arithmetic progression
(2) the first member is 10; the second is 12
Last edited by stolyar on 12 Jul 2004, 03:11, edited 1 time in total.



Senior Manager
Joined: 19 May 2004
Posts: 291

Assuming you ment an arithmetic progression,
With both statements together you can have a clue about the dispersal.
So i say... C.



Manager
Joined: 08 Jun 2004
Posts: 245
Location: INDIA

ans is C ...
a) sayz arithmetic progression ... that could be from any nuber as the beginning number...
B) first =10 and the next 12 we don't know what could be the next and the next untill the last...
combining both we have the 10 28 as the set and we can have the ans ...
hope that helps !
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Director
Joined: 05 Jul 2004
Posts: 894

I guess question asks to find SD.
Numbers are: 10, 12, 14, 16, 18, 20, 22, 24, 26, 28
Mean: 19
SD^2 = 2(81 + 49 + 25 + 9 + 1)/10 = 33
SD roughly 5.7



Senior Manager
Joined: 19 May 2004
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jpv, on DS questions you are not required to give a final answer.
Don't waste your time.



Director
Joined: 05 May 2004
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Location: San Jose, CA

stolyar wrote: Find the standard deviation of tenmember set Y.
(1) the set is an arithmetic progression (2) the first member is 10; the second is 12
C
1 & 2 together defines the sample space



Director
Joined: 14 Jul 2004
Posts: 698

Stolyar: What is the Official Answer? I got C. Combining Statement 1 and statement 2, you'll have all the params needed to find the SD



Senior Manager
Joined: 07 Oct 2003
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Location: Manhattan

stolyar wrote: Find the standard deviation of tenmember set Y.
(1) the set is an arithmetic progression (2) the first member is 10; the second is 12
What's a definition of arithmetic progression?
can it be that the numbers are simply n+2, producing:
10, 12, 14, 16, etc.
or, would n*1.2 also qualify, producing:
10, 12, 14.4, etc..
the answer to the second question determines the answer here



Senior Manager
Joined: 25 Dec 2003
Posts: 359
Location: India

In my opnion the answer is E.
I have a question, perhaps, it may sound crazy. Does arthemetic progression always mean an addition. Can it not be any formulae. In that case,
Statement A  does not give much of an info on what type of arthemetic progression.
Statement B also does not provide any information on how the other numbers wud be.
Hence E. Correct me, if my understading on the the arthemetic progression is wrong.
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Director
Joined: 20 Jul 2004
Posts: 592

arsen/lastochka,
Arithmetic Progression:
Numbers in sequence that have a common difference.
Eg: 2, 4, 6, 8...
1, 3, 7, 10....
In general, a, a+d, a+2d, a+3d....
Geometric Progression:
Numbers in sequence that have a common ratio.
Eg: 2, 4, 8, 16...
1, 3, 9, 27....
In general, a, ar, ar^2, ar^3....
Geometric Progression:
Numbers in sequence that have a common reciprocal ratio (not sure of the term is correct)
Eg: 1/2, 1/4, 1/6, 1/8...
In general, 1/a, 1/a+d, 1/a+2d, 1/a+3d...



CIO
Joined: 09 Mar 2003
Posts: 463

hardworker_indian wrote: arsen/lastochka,
Arithmetic Progression: Numbers in sequence that have a common difference. Eg: 2, 4, 6, 8... 1, 3, 7, 10.... In general, a, a+d, a+2d, a+3d....
Geometric Progression: Numbers in sequence that have a common ratio. Eg: 2, 4, 8, 16... 1, 3, 9, 27.... In general, a, ar, ar^2, ar^3....
Geometric Progression: Numbers in sequence that have a common reciprocal ratio (not sure of the term is correct) Eg: 1/2, 1/4, 1/6, 1/8... In general, 1/a, 1/a+d, 1/a+2d, 1/a+3d...
that's exactly right. arithmetic progression always means common difference between the numbers in the set.










