Author 
Message 
TAGS:

Hide Tags

Intern
Joined: 08 Mar 2011
Posts: 22

Set A consists of all prime numbers between 10 and 25; Set B
[#permalink]
Show Tags
Updated on: 16 Jun 2013, 11:46
Question Stats:
65% (01:03) correct 35% (01:13) wrong based on 484 sessions
HideShow timer Statistics
Set A consists of all prime numbers between 10 and 25; Set B consists of consecutive even integers, and set C consists of consecutive multiples of 7. If all the three sets have an equal number of terms, which of the following represents the ranking of these sets in an ascending order of the standard deviation? (A) C, A, B (B) A, B, C (C) C, B, A (D) B, C, A (E) B, A, C
Official Answer and Stats are available only to registered users. Register/ Login.
Originally posted by punyadeep on 14 Mar 2011, 09:05.
Last edited by Bunuel on 16 Jun 2013, 11:46, edited 1 time in total.
OA added.




Math Expert
Joined: 02 Sep 2009
Posts: 48067

Re: standard deviation
[#permalink]
Show Tags
14 Mar 2011, 09:43
punyadeep wrote: Set A consists of all prime numbers between 10 and 25; Set B consists of consecutive even integers, and set C consists of consecutive multiples of 7. If all the three sets have an equal number of terms, which of the following represents the ranking of these sets in an ascending order of the standard deviation?
(A) C, A, B (B) A, B, C (C) C, B, A (D) B, C, A (E) B, A, C Set A  {11, 13, 17, 19, 23}; Set B  {5 consecutive even integers}, for example  {12, 14, 16, 18, 20}; Set C  {5 consecutive multiples of 7}, for example  {7, 14, 21, 28, 35}. Now, the standard deviation of a set shows how much variation there is from the mean, how widespread a given set is. So, a low standard deviation indicates that the data points tend to be very close to the mean, whereas high standard deviation indicates that the data are spread out over a large range of values. You can see that set C is most widespread and set B is least widespread, so the correct answer is: B, A, C. Answer: E.
_________________
New to the Math Forum? Please read this: Ultimate GMAT Quantitative Megathread  All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics




Intern
Joined: 08 Mar 2011
Posts: 22

Re: standard deviation
[#permalink]
Show Tags
14 Mar 2011, 09:59
thnx so much..........oa is incorrect then...!!



Retired Moderator
Joined: 16 Nov 2010
Posts: 1458
Location: United States (IN)
Concentration: Strategy, Technology

Re: standard deviation
[#permalink]
Show Tags
14 Mar 2011, 19:37
A> 11,13,17,19,23 B> 0,2,4,6,8 C > 7,14,21,28,35 So the answer is E, as C hax maximum gap between elements, and A has slightly more than B because of the last number  23. The OA seems to be wrong. Just curious to know where is this question from; I've seen two SD questions with wrong OA now.
_________________
Formula of Life > Achievement/Potential = k * Happiness (where k is a constant)
GMAT Club Premium Membership  big benefits and savings



Intern
Joined: 08 Mar 2011
Posts: 22

Re: standard deviation
[#permalink]
Show Tags
14 Mar 2011, 19:45
the question is from 700800 level questions.........however there is no source,,,if u wish i can upload the document cos i find this document very good...!!!



Director
Status: Impossible is not a fact. It's an opinion. It's a dare. Impossible is nothing.
Affiliations: University of Chicago Booth School of Business
Joined: 03 Feb 2011
Posts: 787

Re: standard deviation
[#permalink]
Show Tags
15 Mar 2011, 07:10
SD will be high if the sample is not compact since SD is a measure of compactness.
Mean will fall in the middle of the highest and lowest. So more the distance from the mean  the higher the SD. Assuming all the data is positive the SD will be proportional to the range (highest  smallest)
Set A {11 13 17 19 23} range = 12 Se B {12 14 16 18 20} range = 8 Set C {14 21 28 35 42 } range = 28
SD(B) < SD(A) < SD(C)
Please correct me if this reasoning is wrong.



Director
Status: Up again.
Joined: 31 Oct 2010
Posts: 514
Concentration: Strategy, Operations
GMAT 1: 710 Q48 V40 GMAT 2: 740 Q49 V42

Re: standard deviation
[#permalink]
Show Tags
15 Mar 2011, 10:19
punyadeep wrote: the question is from 700800 level questions.........however there is no source,,,if u wish i can upload the document cos i find this document very good...!!! Just my 2 cents: there are a lot of "good" documents around.. but least we can do is be careful on our part. If others didnt testify the right answer, I would have missed my dinner! Edit: I just found out, this question is from Veritas Prep "Statistics and Problem Solving" book and the OA is indeed E.
_________________
My GMAT debrief: http://gmatclub.com/forum/from620to710mygmatjourney114437.html



Retired Moderator
Joined: 20 Dec 2010
Posts: 1877

Re: standard deviation
[#permalink]
Show Tags
15 Mar 2011, 10:27
punyadeep wrote: the question is from 700800 level questions.........however there is no source,,,if u wish i can upload the document cos i find this document very good...!!! Please do so. thanks.
_________________
~fluke
GMAT Club Premium Membership  big benefits and savings



Intern
Joined: 08 Mar 2011
Posts: 22

Re: standard deviation
[#permalink]
Show Tags
16 Mar 2011, 06:45
@ fluke...two documents iam uploading......they were sent to me by a frnd who scored 750 and he just went through this document for quant twice.......i found it focussed and helpful too...!!



Intern
Joined: 08 Mar 2011
Posts: 22

Re: standard deviation
[#permalink]
Show Tags
16 Mar 2011, 06:48
@ fluke...here r the answwers to it...!!
Attachments
File comment: answers with detailed explanations
BIBLE SOLUTIONS.pdf [1.95 MiB]
Downloaded 2424 times



Math Expert
Joined: 02 Sep 2009
Posts: 48067

Re: Set A consists of all prime numbers between 10 and 25; Set B
[#permalink]
Show Tags
12 Jul 2013, 02:35



Verbal Forum Moderator
Joined: 10 Oct 2012
Posts: 615

Re: Set A consists of all prime numbers between 10 and 25; Set B
[#permalink]
Show Tags
Updated on: 12 Jul 2013, 13:03
punyadeep wrote: Set A consists of all prime numbers between 10 and 25; Set B consists of consecutive even integers, and set C consists of consecutive multiples of 7. If all the three sets have an equal number of terms, which of the following represents the ranking of these sets in an ascending order of the standard deviation?
(A) C, A, B (B) A, B, C (C) C, B, A (D) B, C, A (E) B, A, C Set A \(\to {11,13,17,19,23}\) Fact: Addition/subtraction of any number from a given set doesn't change the S.D of the given set. From Set A, subtract 11 across to represent \(Set A^'\) as \(\to {0,2,6,8,12}\). \(S.D of Set A = S.D of Set A^'\) If you notice closely, Set \(A^'\) is very close to Set B, just that Set B looks like \(\to{0,2,4,6,8}\),i.e. a datapoint of 12 is present instead of 4, which makes \(Set A^'\) more spreadout then Set B. Thus, \(S.D of Set B< S.D of Set A^'\) Assume Set C\(\to {0,7,14,21,28}\) S.D represents how far are the data points are from the mean of the set, we can see that Set C has the most spreadout data points and the correct order = B,A,C. E.
_________________
All that is equal and notDeep Dive Inequality
Hit and Trial for Integral Solutions
Originally posted by mau5 on 12 Jul 2013, 10:28.
Last edited by mau5 on 12 Jul 2013, 13:03, edited 1 time in total.



Director
Joined: 14 Dec 2012
Posts: 806
Location: India
Concentration: General Management, Operations
GPA: 3.6

Re: Set A consists of all prime numbers between 10 and 25; Set B
[#permalink]
Show Tags
12 Jul 2013, 10:47
punyadeep wrote: Set A consists of all prime numbers between 10 and 25; Set B consists of consecutive even integers, and set C consists of consecutive multiples of 7. If all the three sets have an equal number of terms, which of the following represents the ranking of these sets in an ascending order of the standard deviation?
(A) C, A, B (B) A, B, C (C) C, B, A (D) B, C, A (E) B, A, C Hi, few things to keep in mind. =>std deviation depends on distance of each term from mean and number of terms.==>since number of terms are same..we are concerned only about distance of EACH TERM from MEAN.==more the distance more the deviation. =>std deviation is always positive==>so not concerned whether numbers are positive or negative. SET A==>(11,13,17,19,23)==>avg around 16==>you can see distance of 11,13,17,19,23 is 5,3,1,3,7....1) SET B==>(CONSECUTIVE EVEN INTEGERS...)= ( N4,N2,N,N+2,N+4)===>mean=N==>DISTANCE FROM MEAN= 4,2,0,2,4 SET C==>MULTIPLES OF 7 ====N14,N7,N,N+7,N+14===>MEAN=N====>DISTANCE FROM MEAN=14,7,0,7,14. if we compare all distance clearly we can say B<A<C===>HENCE OPTION E
_________________
When you want to succeed as bad as you want to breathe ...then you will be successfull....
GIVE VALUE TO OFFICIAL QUESTIONS...
GMAT RCs VOCABULARY LIST: http://gmatclub.com/forum/vocabularylistforgmatreadingcomprehension155228.html learn AWA writing techniques while watching video : http://www.gmatprepnow.com/module/gmatanalyticalwritingassessment : http://www.youtube.com/watch?v=APt9ITygGss



Intern
Joined: 09 Dec 2014
Posts: 46
GMAT 1: 600 Q42 V32 GMAT 2: 710 Q48 V38
GPA: 3.7

Re: Set A consists of all prime numbers between 10 and 25; Set B
[#permalink]
Show Tags
30 Dec 2015, 00:24
gmat1220 wrote: SD will be high if the sample is not compact since SD is a measure of compactness.
Mean will fall in the middle of the highest and lowest. So more the distance from the mean  the higher the SD. Assuming all the data is positive the SD will be proportional to the range (highest  smallest)
Set A {11 13 17 19 23} range = 12 Se B {12 14 16 18 20} range = 8 Set C {14 21 28 35 42 } range = 28
SD(B) < SD(A) < SD(C)
Please correct me if this reasoning is wrong. Buneal, please could you provide more info on how the standard deviation is proportional to the range. Is this strategy useful when you are in stressed conditions? Thanks in Advance



NonHuman User
Joined: 09 Sep 2013
Posts: 7770

Re: Set A consists of all prime numbers between 10 and 25; Set B
[#permalink]
Show Tags
25 Jul 2018, 22:08
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources




Re: Set A consists of all prime numbers between 10 and 25; Set B &nbs
[#permalink]
25 Jul 2018, 22:08






