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# Find the standard deviation of ten-member set Y. (1) the set

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SVP
Joined: 03 Feb 2003
Posts: 1604
Find the standard deviation of ten-member set Y. (1) the set [#permalink]

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12 Jul 2004, 00:53
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Find the standard deviation of ten-member 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

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12 Jul 2004, 01:40
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

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12 Jul 2004, 05:26
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 !

Have fun
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Director
Joined: 05 Jul 2004
Posts: 894

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12 Jul 2004, 07:50
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
Posts: 291

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12 Jul 2004, 09:21
jpv, on DS questions you are not required to give a final answer.
Director
Joined: 05 May 2004
Posts: 574
Location: San Jose, CA

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12 Jul 2004, 10:30
stolyar wrote:
Find the standard deviation of ten-member 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

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17 Aug 2004, 18:15
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
Posts: 350
Location: Manhattan

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17 Aug 2004, 20:21
stolyar wrote:
Find the standard deviation of ten-member 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..

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

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17 Aug 2004, 20:43
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

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20 Aug 2004, 01:33
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

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20 Aug 2004, 07:41
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.
20 Aug 2004, 07:41
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