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

It is currently 16 Apr 2014, 17:13

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If sets X and Y have an equal number of elements, does set X

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
Joined: 12 Feb 2012
Posts: 103
Followers: 1

Kudos [?]: 8 [0], given: 28

If sets X and Y have an equal number of elements, does set X [#permalink] New post 29 Jul 2012, 17:43
If sets X and Y have an equal number of elements, does set X have a greater standard deviation than set Y?

(1) The difference between each pair of the neighboring elements is consistent throughout each set;
(2) Each of the first two elements in Set Y is twice greater than the corresponding first and second elements in Set X.

Solution

[Reveal] Spoiler:
Solution:

1) We are told that both sets are arithmetic progressions. Although both sets X and Y have the same number of elements, a very important fact, the statement neither specifies the distributions of the arithmetic sequence for each of the sets NOR a relationship between how the arthimetic progression between the two sets relate. Either would have done. Ex.

X={2,4,6,8,10} A.P. with spacing of 2
Y={5,10,15,20,25} A.P with spacing of 5.

In this case Y has a higher standard deviation(large spacing) than X. The reverse could be flipped:

X={6,12,18,24,30} A.P. with spacing of 6
Y={5,10,15,20,25} A.P with spacing of 5.

In this case X has a higher standard deviation(large spacing) than Y.

2) Doesn't tell us how the numbers after the first two terms play out. Ex:

X={3,7,10000}
Y={6,14,20}

X has the larger SD in this example.

X={3,7,5}
Y={6,14,2000}

Y has the larger SD in this example.

Hence INSUFF

(1) & (2)

AP for both sets and Y doubles the first two elements of X.

X={a,a+2,a+4,.....} spacing of 2
Y={2a,2a+4,2a+6....} spacing of 4 imposed on all the numbers since we have an A.P.

Notice we now have a relationship between the two sets. The spacing for Y is double that of X. Hence SUFF.
2 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 17283
Followers: 2868

Kudos [?]: 18334 [2] , given: 2345

GMAT Tests User CAT Tests
Re: Standard Deviation [#permalink] New post 30 Jul 2012, 00:35
2
This post received
KUDOS
Expert's post
The wording of this question is quite ambiguous and non-GMAT like:

1. Sets are not ordered by definition. So, "the first two elements in Set" doesn't make any sense.
2. "Twice greater" and "consistent throughout each set" is not the wording you'll see on the GMAT.

So, I wouldn't worry about this question at all.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

Manager
Manager
Joined: 12 Feb 2012
Posts: 103
Followers: 1

Kudos [?]: 8 [0], given: 28

Re: Standard Deviation [#permalink] New post 01 Aug 2012, 17:44
Bunuel wrote:
The wording of this question is quite ambiguous and non-GMAT like:

1. Sets are not ordered by definition. So, "the first two elements in Set" doesn't make any sense.
2. "Twice greater" and "consistent throughout each set" is not the wording you'll see on the GMAT.

So, I wouldn't worry about this question at all.


Your absolutly right! That slipped my mind. Nonetheless the writer of the questions intent was that the set is sequntielly ordered. If that were the case the answer would be (C)
Re: Standard Deviation   [#permalink] 01 Aug 2012, 17:44
    Similar topics Author Replies Last post
Similar
Topics:
Popular new posts Set X consists of 9 positive elements. Set Y consists of the kevincan 17 12 Jul 2006, 15:37
Popular new posts Set X consists of 9 positive elements. Set Y consists of the kevincan 19 19 Sep 2006, 12:49
New posts Experts publish their posts in the topic 4/5 of the elements in set D are equal to x, and the marcodonzelli 7 25 Jan 2008, 09:14
New posts Experts publish their posts in the topic How many elements does number set N have? (1) Ten of the ritula 9 26 Jun 2008, 23:29
New posts 6 Experts publish their posts in the topic Set X consists of 9 positive elements. Set Y consists of the nitya34 7 10 Mar 2009, 20:30
Display posts from previous: Sort by

If sets X and Y have an equal number of elements, does set X

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

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®.