Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 18 Jun 2013, 20:12

# Range & SD (m03q34)

Author Message
Senior Manager
Joined: 05 Oct 2008
Posts: 283
Followers: 3

Kudos [?]: 18 [2] , given: 22

Range & SD (m03q34) [#permalink]  26 Oct 2008, 23:39
2
KUDOS
00:00

Question Stats:

87% (01:46) correct 12% (00:22) wrong based on 82 sessions
Which set(s) has the greatest standard deviation?

1. Set 1 consisting of 10 digits
2. Set 2 consisting of 10 first positive consecutive even numbers
3. Set 3 consisting of 10 first primes

(A) set 1
(B) set 2
(C) set 3
(D) set 1 and 2
(E) set 1, 2, and 3

[Reveal] Spoiler: OA
C

Source: GMAT Club Tests - hardest GMAT questions
[Reveal] Spoiler: OA
 Kaplan Promo Code Knewton GMAT Discount Codes GMAT Pill GMAT Discount Codes
Senior Manager
Joined: 28 Feb 2007
Posts: 317
Followers: 1

Kudos [?]: 20 [0], given: 0

Re: Range & SD [#permalink]  27 Oct 2008, 01:25
C.
all other things being equal. set of #s with greater differences has the greatest SD.
Manager
Joined: 28 Jul 2004
Posts: 142
Location: Melbourne
Schools: Yale SOM, Tuck, Ross, IESE, HEC, Johnson, Booth
Followers: 1

Kudos [?]: 5 [0], given: 2

Re: Range & SD [#permalink]  27 Oct 2008, 06:53
How do you know that 10 digits in set 1 are not widely distributed as those in the set of prime numbers. There is no info which tells us this. S1 can be [1,2.....9,10] or [1,4, 23, 56,......1234] or anything else.
_________________

kris

Senior Manager
Joined: 28 Feb 2007
Posts: 317
Followers: 1

Kudos [?]: 20 [1] , given: 0

Re: Range & SD [#permalink]  27 Oct 2008, 11:15
1
KUDOS
Krishan,
what I know about digits (in this context) is they are 10 numbers that form other numbers: {0,1,2,3,4,5,6,7,8,9}
Senior Manager
Joined: 05 Oct 2008
Posts: 283
Followers: 3

Kudos [?]: 18 [0], given: 22

Re: Range & SD [#permalink]  29 Oct 2008, 08:56
Krishan,

That is exactly my question...

Can anyone pls explain how do we know what digits are to be selected for set one?
Intern
Joined: 30 Aug 2010
Posts: 24
Followers: 0

Kudos [?]: 0 [0], given: 2

Re: Range & SD (m03q34) [#permalink]  06 Oct 2010, 08:35
yes digit refers to number 0 through 9. The number 10 would be a two-digit number (1 and 0 being digits).

As such, a set of 10 digits would be consecutive in order to maximize the standard deviation (we only have ten digits to choose from [0 through 9] so any identical digits in the set would minimize the overall standard deviation of the set).

So, the max standard deviation for set 1 = 1

Set 2 = 2

Set 3 is more than 2 (no need to do the standard deviation calculations, especially on GMAT since it tests only that you know the concept of what it is) when you start getting into the bold parts of the set:

2,3,5,7,11,13,17,,19,21,23

Set three has highest standard deviation, as there are 4 numbers with 4 units between them
Manager
Status: He who asks is a fool for five minutes, but he who does not ask remains a fool forever
Joined: 20 Aug 2010
Posts: 104
Followers: 2

Kudos [?]: 2 [0], given: 2

Re: Range & SD (m03q34) [#permalink]  06 Oct 2010, 08:49

Reason for my choice : In case of SD, the more the difference between numbers mean and number , highest the SD. So in case of C we have the highest SD
Intern
Joined: 12 Jul 2010
Posts: 37
Location: Minnesota
Schools: Wisconsin, Carlson, McCombs, Ross, Stern
Followers: 1

Kudos [?]: 4 [0], given: 1

Re: Range & SD (m03q34) [#permalink]  06 Oct 2010, 09:14
The question would have been more clear (i.e. more GMAT-like) if statement 1 said:

1. Set 1 consisting of 10 single-digit integers.

That being said, C is clearly the correct answer...

First 10 primes are 2, 3, 5, 7, 11, 13, 17, 23, 29, and 31.
First 10 positive consecutive even integers are 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20.

If you think about standard deviation as the "average difference between each number" (not technically true but sufficient for GMAT purposes) then the set of primes beats the set of even integers.
Senior Manager
Status: Time to step up the tempo
Joined: 24 Jun 2010
Posts: 418
Location: Milky way
Schools: ISB, Tepper - CMU, Chicago Booth, LSB
Followers: 6

Kudos [?]: 75 [0], given: 50

Re: Range & SD (m03q34) [#permalink]  06 Oct 2010, 10:20

Only C with its set of 10 primes numbers are spaced widely apart and hence its variance and S.D is the highest.
_________________

Support GMAT Club by putting a GMAT Club badge on your blog

Senior Manager
Joined: 06 Jun 2009
Posts: 335
Location: USA
WE 1: Engineering
Followers: 1

Kudos [?]: 36 [0], given: 0

Re: Range & SD (m03q34) [#permalink]  06 Oct 2010, 10:38
abushey31 wrote:
The question would have been more clear (i.e. more GMAT-like) if statement 1 said:

1. Set 1 consisting of 10 single-digit integers.

That being said, C is clearly the correct answer...

First 10 primes are 2, 3, 5, 7, 11, 13, 17, 23, 29, and 31.
First 10 positive consecutive even integers are 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20.

If you think about standard deviation as the "average difference between each number" (not technically true but sufficient for GMAT purposes) then the set of primes beats the set of even integers.

Depends. There are numbers and there are digits. Numbers are made of digits ! Actually, there are only 10 digits in Mathematics.
_________________

All things are possible to those who believe.

Manager
Joined: 08 Sep 2010
Posts: 241
Location: India
WE 1: 6 Year, Telecom(GSM)
Followers: 3

Kudos [?]: 39 [0], given: 21

Re: Range & SD (m03q34) [#permalink]  06 Oct 2010, 10:42
It was easy but after understanding the !st point.Good one.Considered for KUDOS
Intern
Joined: 12 Jul 2010
Posts: 37
Location: Minnesota
Schools: Wisconsin, Carlson, McCombs, Ross, Stern
Followers: 1

Kudos [?]: 4 [0], given: 1

Re: Range & SD (m03q34) [#permalink]  06 Oct 2010, 11:05
abushey31 wrote:
The question would have been more clear (i.e. more GMAT-like) if statement 1 said:

1. Set 1 consisting of 10 single-digit integers.

That being said, C is clearly the correct answer...

First 10 primes are 2, 3, 5, 7, 11, 13, 17, 23, 29, and 31.
First 10 positive consecutive even integers are 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20.

If you think about standard deviation as the "average difference between each number" (not technically true but sufficient for GMAT purposes) then the set of primes beats the set of even integers.

Depends. There are numbers and there are digits. Numbers are made of digits ! Actually, there are only 10 digits in Mathematics.

Right. My point is that by definition Sets contain numbers or variables...saying that a set contains digits is not mathematically clear. Given the way the rest of the question is worded you can reason that that's what the creator of the question meant, but on a real GMAT question it should be more clear in my opinion.
Senior Manager
Joined: 06 Jun 2009
Posts: 335
Location: USA
WE 1: Engineering
Followers: 1

Kudos [?]: 36 [0], given: 0

Re: Range & SD (m03q34) [#permalink]  06 Oct 2010, 11:11
abushey31 wrote:
abushey31 wrote:
The question would have been more clear (i.e. more GMAT-like) if statement 1 said:

1. Set 1 consisting of 10 single-digit integers.

That being said, C is clearly the correct answer...

First 10 primes are 2, 3, 5, 7, 11, 13, 17, 23, 29, and 31.
First 10 positive consecutive even integers are 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20.

If you think about standard deviation as the "average difference between each number" (not technically true but sufficient for GMAT purposes) then the set of primes beats the set of even integers.

Depends. There are numbers and there are digits. Numbers are made of digits ! Actually, there are only 10 digits in Mathematics.

Right. My point is that by definition Sets contain numbers or variables...saying that a set contains digits is not mathematically clear. Given the way the rest of the question is worded you can reason that that's what the creator of the question meant, but on a real GMAT question it should be more clear in my opinion.

I believe this is all part of the GMAT trick. A lot of the questions are missed because they are misunderstood. I agree with you, but I guess we have to get use to these tricks. Or at the least, see how we can be tricked.

Good Luck !
_________________

All things are possible to those who believe.

Intern
Joined: 01 Oct 2010
Posts: 5
Followers: 0

Kudos [?]: 8 [0], given: 1

Re: Range & SD (m03q34) [#permalink]  07 Oct 2010, 03:27

Set 1 ={0,1,2,3,4,5,6,7,8,9} i.e 10 digits
Set 2 ={ 2,4,6,8,10,12,14,16,18,20}
Set 3 ={2,3,5,7,11,13,17,19,23,29}

The S.D is higher for the series that has a higher range...

Just had a little doubt about the first set hope its correct.
Manager
Joined: 07 Aug 2010
Posts: 89
Followers: 1

Kudos [?]: 13 [0], given: 9

Re: Range & SD (m03q34) [#permalink]  07 Oct 2010, 12:23
Agree on the first set ambiguity. could be more cleare - set 1 consisting of the first 10 digits.

_________________

Click that thing - Give kudos if u like this

Manager
Joined: 07 Jan 2010
Posts: 151
Location: So. CA
WE 1: 2 IT
WE 2: 4 Software Analyst
Followers: 2

Kudos [?]: 6 [0], given: 57

Re: Range & SD (m03q34) [#permalink]  07 Oct 2010, 18:36
hmmmm i don't see much ambiguity with set 1, it doesn't say first 10 digits. All it says is "Set 1 consisting of 10 digits" which can mean anything. Given with that kind of info, I automatically knocked it out.
Manager
Joined: 16 Sep 2010
Posts: 230
Location: United States
Concentration: Finance, Real Estate
GMAT 1: 740 Q48 V42
Followers: 6

Kudos [?]: 42 [0], given: 2

Re: Range & SD (m03q34) [#permalink]  13 Oct 2010, 20:30
Should be C. Although A in theory could be it as its 10 random digits. But C is the only one that is explicitly correct.
Intern
Status: Preparing again for second attempt....
Joined: 11 Dec 2010
Posts: 24
Location: Pune, India
WE 1: 6 years
Followers: 0

Kudos [?]: 3 [0], given: 2

Re: Range & SD (m03q34) [#permalink]  10 Oct 2011, 05:29
Just to add in my point of looking at such questions. Stat2 & 3 are quite clear to everyone, so let me talk only about stat1.

Stmt1: Set 1 is 10 digits. There are two ways to knock this option off.

First, 'a digit' is always a single digit and thus can only be -9, -8, -7 .. to 7,8,9. You can assume that your number is a two-digit or three-digit, only when it is stated explicitly or when it is stated that the number is not a single digit number.

Second way of knocking this off (incase there is confusion on deciding what a digit can be), is to think of the statement in such a way that it holds true under all circumstances. That is, if you chose your numbers 2,3,4...consecutively, then you know your std deviation will be lesser than that of stmt3. However, if you chose your numbers as 1, 100, 3456, 46752, .... so on, you know it will yield a std deviation larger than stmt3.

Thus you will never be in a position to say that stmt will always be true. Hence it is incorrect.

Consider kudos if you liked my explanation...
Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2098
Followers: 109

Kudos [?]: 664 [0], given: 376

Re: Range & SD (m03q34) [#permalink]  10 Oct 2011, 08:46
study wrote:
Which set(s) has the greatest standard deviation?

1. Set 1 consisting of 10 digits
2. Set 2 consisting of 10 first positive consecutive even numbers
3. Set 3 consisting of 10 first primes

(A) set 1
(B) set 2
(C) set 3
(D) set 1 and 2
(E) set 1, 2, and 3

[Reveal] Spoiler: OA
C

Source: GMAT Club Tests - hardest GMAT questions

A digit in GMAT is always a non-negative single-digit integer

Valid digits={0,1,2,3,4,5,6,7,8,9}

1. Set 1 consisting of 10 digits
{0,0,0,0,9,9,9,9}- Believe this will give us the max deviation: 4.5

2. Set 2 consisting of 10 first positive consecutive even numbers
{2,4,6,8,10,12,14,16,18,20}
Diff= 9,7,5,3,1,1,3,5,7,9

3. Set 3 consisting of 10 first primes
{3,5,7,11,13,17,19,23,29}. Mean=12 Approx
Diff= 9,7,5,1,1,5,7,11,17
These numbers are bigger than their counterpart in 2. Deviation must be greater thus.

Ans: "C"
_________________
Senior Manager
Status: Kick Ass Gmat
Affiliations: Trained Stage Actor,First aider,Swimmer,Sketch artist,Writer
Joined: 28 Jun 2011
Posts: 418
Location: India
Concentration: Finance, General Management
GMAT Date: 11-12-2013
GPA: 3.5
WE: Consulting (Human Resources)
Followers: 12

Kudos [?]: 26 [0], given: 32

Re: Range & SD (m03q34) [#permalink]  24 Nov 2011, 15:00
Standard deviation is about the variety of range a set can expand....

For ex- set a got (2 4 6 8)

Set B got (2 5 7 11)

B got the greater SD...
_________________

Dont look for the wrong thing that you have done rather find remedies.

Indian Bschools Accepting Gmat--> indian-b-schools-accepting-gmat-scores-82525.html

My Gmat Daily Diary--> how-much-time-should-i-spend-120796.html

Mba Ranking 2013--> all-2013-mba-rankings-99812.html

How to Convert Indian GPA/ Percentage to US 4 pt. GPA scale--> how-to-convert-indian-gpa-percentage-to-us-4-pt-gpa-scale-124249.html

POWERSCORE CRITICAL REASONING BIBLE - FULL CHAPTER NOTES --> powerscore-critical-reasoning-bible-full-chapter-notes-115864.html

Result correlation between GMAT and GMAT Club's Tests -->http://gmatclub.com/forum/result-correlation-between-gmat-and-gmat-club-s-tests-30989.html

Best GMAT Stories - Period! --> best-gmat-stories-period-98512.html

----
---
--
-

Kick Ass Gmat

Re: Range & SD (m03q34)   [#permalink] 24 Nov 2011, 15:00
Similar topics Replies Last post
Similar
Topics:
Range 1 30 Jul 2003, 20:57
SD-MEAN 2 14 Oct 2008, 20:51
SD 1 27 Jun 2009, 21:56
3 Range & SD (m03q34) 21 26 Oct 2008, 23:39
2 SD 2 29 May 2011, 11:16
Display posts from previous: Sort by

# Range & SD (m03q34)

 Go to page    1   2    Next  [ 22 posts ]

Moderator: Bunuel

 Powered by phpBB © phpBB Group and phpBB SEO Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.