Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 39622

A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
11 Sep 2012, 04:50
Question Stats:
76% (01:35) correct
24% (00:42) wrong based on 1012 sessions
HideShow timer Statistics



Math Expert
Joined: 02 Sep 2009
Posts: 39622

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
11 Sep 2012, 04:50
2
This post received KUDOS
Expert's post
8
This post was BOOKMARKED
SOLUTIONA scientist recorded the number of eggs in each of 10 birds' nests. What was the standard deviation of the numbers of eggs in the 10 nests?The standard deviation of a set is always more than or equal to zero (\(SD\geq{0}\)). The standard deviation is 0 only when a set contains all identical elements (or which is same only 1 element). (1) The average (arithmetic mean) number of eggs for the 10 nests was 4. Knowing the average does not help to get the standard deviation. Not sufficient. (2) Each of the 10 nests contained the same number of eggs. So, the set contains all identical elements, which means that the standard deviation is zero. Sufficient. Answer: B.
_________________
New to the Math Forum? Please read this: 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: 12 Jun 2012
Posts: 41

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
11 Sep 2012, 08:13
2
This post received KUDOS
scientist recorded the number of eggs in each of 10 birds' nests. What was the standard deviation of the numbers of eggs in the 10 nests? (1) The average (arithmetic mean) number of eggs for the 10 nests was 4. (2) Each of the 10 nests contained the same number of eggs. SD = Sqrt( sum(xMean)^2/n) 1 is INEFF as we can take two samples, sample one 5 nests were 3 and 5 nests were 5  arithmetic means = 4. another sample, 5 nests are 2 and 5 nests are 6, arithmetic mean 4 again but standard deviation (the dispersion of data points) is larger 2 is GOOD as the SD = 0, if all the same, no dispersion, Answer is B
_________________
If you find my post helpful, please GIVE ME SOME KUDOS!



Senior Manager
Joined: 15 Jun 2010
Posts: 361
Schools: IE'14, ISB'14, Kellogg'15
WE 1: 7 Yrs in Automobile (Commercial Vehicle industry)

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
12 Sep 2012, 04:02
2
This post received KUDOS
Bunuel wrote: A scientist recorded the number of eggs in each of 10 birds' nests. What was the standard deviation of the numbers of eggs in the 10 nests?
(1) The average (arithmetic mean) number of eggs for the 10 nests was 4. (2) Each of the 10 nests contained the same number of eggs.
St 1: Insufficient: Avg no of eggs for 10 nest is 4. ie total no of eggs are 40. So we can distribute it in 10 nests in various combinations. Hence the SD will vary accordingly. St 2: Sufficient: Since each nest contains same no of eggs the SD is "0" Hence Answer is B
_________________
Regards SD  Press Kudos if you like my post. Debrief 610540580710(Long Journey): http://gmatclub.com/forum/from600540580710finallyachievedin4thattempt142456.html



Director
Joined: 24 Aug 2009
Posts: 503
Schools: Harvard, Columbia, Stern, Booth, LSB,

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
12 Sep 2012, 13:20
1
This post received KUDOS
The question can be simplified to " What is distribution of Eggs in 10 nests from the mean no of eggs" Statement 1 Mean is given but no information is given regarding the distribution around mean.> Insufficient. Statement 2 As each nest contain the same no of eggs, there is '0' distribution around mean.>Sufficient. Answer B Hope it helps
_________________
If you like my Question/Explanation or the contribution, Kindly appreciate by pressing KUDOS. Kudos always maximizes GMATCLUB worth Game Theory
If you have any question regarding my post, kindly pm me or else I won't be able to reply



Math Expert
Joined: 02 Sep 2009
Posts: 39622

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
14 Sep 2012, 06:31
SOLUTIONA scientist recorded the number of eggs in each of 10 birds' nests. What was the standard deviation of the numbers of eggs in the 10 nests?The standard deviation of a set is always more than or equal to zero (\(SD\geq{0}\)). The standard deviation is 0 only when a set contains all identical elements (or which is same only 1 element). (1) The average (arithmetic mean) number of eggs for the 10 nests was 4. Knowing the average does not help to get the standard deviation. Not sufficient. (2) Each of the 10 nests contained the same number of eggs. So, the set contains all identical elements, which means that the standard deviation is zero. Sufficient. Answer: B. Kudos points given to everyone with correct solution. Let me know if I missed someone.
_________________
New to the Math Forum? Please read this: 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 Jan 2013
Posts: 1

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
23 Jan 2013, 08:29
A scientist recorded the number of eggs in each of 10 bird's nests. What was the standard deviation of the numbers of eggs in the 10 nests?
(1) The average(arithmetic mean) number of eggs for the 10 nests was 4. (2) Each of the 10 nests contained the same number of eggs. 
This question does not make sense to me. Isn't the question selfsufficient? The scientist recorded the number of eggs in each of 10 nests. so he/she can calculate the average and standard deviation as well. Why does he/she need (1) or (2) ?



Math Expert
Joined: 02 Sep 2009
Posts: 39622

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
23 Jan 2013, 08:35
slifedt wrote: A scientist recorded the number of eggs in each of 10 bird's nests. What was the standard deviation of the numbers of eggs in the 10 nests?
(1) The average(arithmetic mean) number of eggs for the 10 nests was 4. (2) Each of the 10 nests contained the same number of eggs. 
This question does not make sense to me. Isn't the question selfsufficient? The scientist recorded the number of eggs in each of 10 nests. so he/she can calculate the average and standard deviation as well. Why does he/she need (1) or (2) ? Merging similar topics. Pleas refer to the solutions above. As for your doubt, the statements are sufficient if WE can calculate SD based on the info given not the scientist. P.S. Please read carefully and follow: rulesforpostingpleasereadthisbeforeposting133935.html Pay attention to the rule #3: the name of a topic (subject field) MUST be the first 40 characters (~the first two sentences) of the question.
_________________
New to the Math Forum? Please read this: 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



Manager
Joined: 18 Oct 2011
Posts: 90
Location: United States
Concentration: Entrepreneurship, Marketing
GMAT Date: 01302013
GPA: 3.3

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
24 Jan 2013, 13:19
Statement 1: We know the mean but we don't have any other information to compute the SD. Insufficient. Statement 2: If all the nests contain the same amount of eggs, the mean # of eggs would be the same as # eggs in every nest...no matter how many eggs there are the SD will always be 0. Sufficent.



GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15932

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
01 May 2014, 08:11
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



Manager
Joined: 07 Apr 2014
Posts: 141

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
07 Sep 2014, 01:31
Bunuel wrote: A scientist recorded the number of eggs in each of 10 birds' nests. What was the standard deviation of the numbers of eggs in the 10 nests? (1) The average (arithmetic mean) number of eggs for the 10 nests was 4. (2) Each of the 10 nests contained the same number of eggs. Practice Questions Question: 38 Page: 278 Difficulty: 650 Answer  B.. 1. just mean provided no other data about eggs in each nest.. could be anything. No suff. 2. All nest has same # of egg . Hence SD=0 .. Suff



GMAT Club Legend
Joined: 09 Sep 2013
Posts: 15932

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
06 Dec 2015, 00:06
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



Senior Manager
Joined: 20 Aug 2015
Posts: 396
Location: India

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
07 Dec 2015, 05:07
Bunuel wrote: A scientist recorded the number of eggs in each of 10 birds' nests. What was the standard deviation of the numbers of eggs in the 10 nests?
(1) The average (arithmetic mean) number of eggs for the 10 nests was 4. (2) Each of the 10 nests contained the same number of eggs.
Standard Deviation is the distance of the elements of a set from the mean. Keeping this thing in mind helps solving most of the questions. In majority of the questions, you will not be tested on your knowledge of the formula of SDRequired: standard deviation of the numbers of eggs in the 10 nests Statement 1: The average (arithmetic mean) number of eggs for the 10 nests was 4 This does not tells us anything about the other elements. Hence we cannot find the SD INSUFFICIENTStatement 2: Each of the 10 nests contained the same number of eggs This means that the average = no. of eggs in each nest. Hence the SD = 0 (Distance from average = 0 if all the elements of a set are same) SUFFICIENTOption B
_________________
Reach out to us at bondwithus@gmatify.com



Intern
Joined: 18 Jan 2016
Posts: 2

Date sufficiency [#permalink]
Show Tags
17 Feb 2016, 17:29
A scientist recorded the number of eggs in each of 10 birds' nests. What was the standard deviation of the numbers of eggs in the 10 nests?
(1)The average (arithmetic mean) number of eggs for the 10 nests was 4.
(2)Each of the 10 nests contained the same number of eggs. A Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient. B Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient. C BOTH statement TOGETHER are sufficient, but NEITHER statement ALONE is sufficient. D EACH statement ALONE is sufficient. E Statements (1) and (2) TOGETHER are NOT sufficient.



Math Forum Moderator
Joined: 20 Mar 2014
Posts: 2642
Concentration: Finance, Strategy
GPA: 3.7
WE: Engineering (Aerospace and Defense)

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
17 Feb 2016, 17:39
EmmaShen wrote: A scientist recorded the number of eggs in each of 10 birds' nests. What was the standard deviation of the numbers of eggs in the 10 nests?
(1)The average (arithmetic mean) number of eggs for the 10 nests was 4.
(2)Each of the 10 nests contained the same number of eggs. A Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient. B Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient. C BOTH statement TOGETHER are sufficient, but NEITHER statement ALONE is sufficient. D EACH statement ALONE is sufficient. E Statements (1) and (2) TOGETHER are NOT sufficient. Please search for a question before you start a new thread. This question has already been discussed. Make sure to type in the correct topic title and follow other posting guidelines (link in my signatures). Topics merged.
_________________
Thursday with Ron updated list as of July 1st, 2015: http://gmatclub.com/forum/consolidatedthursdaywithronlistforallthesections201006.html#p1544515 Rules for Posting in Quant Forums: http://gmatclub.com/forum/rulesforpostingpleasereadthisbeforeposting133935.html Writing Mathematical Formulae in your posts: http://gmatclub.com/forum/rulesforpostingpleasereadthisbeforeposting133935.html#p1096628 GMATCLUB Math Book: http://gmatclub.com/forum/gmatmathbookindownloadablepdfformat130609.html Everything Related to Inequalities: http://gmatclub.com/forum/inequalitiesmadeeasy206653.html#p1582891 Inequalities tips: http://gmatclub.com/forum/inequalitiestipsandhints175001.html Debrief, 650 to 750: http://gmatclub.com/forum/650to750a10monthjourneytothescore203190.html



Target Test Prep Representative
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 1044

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]
Show Tags
25 Aug 2016, 16:01
Bunuel wrote: A scientist recorded the number of eggs in each of 10 birds' nests. What was the standard deviation of the numbers of eggs in the 10 nests?
(1) The average (arithmetic mean) number of eggs for the 10 nests was 4. (2) Each of the 10 nests contained the same number of eggs.] We are asked to determine the standard deviation of the number of eggs in 10 nests. Statement One Alone:The average (arithmetic mean) number of eggs for the 10 nests was 4. Knowing only the average of the number of eggs for the 10 nests is not enough information to determine the standard deviation. Statement one is not sufficient to answer the question. We can eliminate answer choices A and D. Statement Two Alone:Each of the 10 nests contained the same number of eggs. Since we know that each nest had the same number of eggs, we know that the standard deviation must be zero. The answer is B.
_________________
Jeffery Miller
Head of GMAT Instruction
GMAT Quant SelfStudy Course
500+ lessons 3000+ practice problems 800+ HD solutions




Re: A scientist recorded the number of eggs in each of 10 birds'
[#permalink]
25 Aug 2016, 16:01








Similar topics 
Author 
Replies 
Last post 
Similar Topics:


11


If Set A consists of 10 numbers, each number reciprocal of a prime num

chetan2u 
10 
22 Jan 2016, 22:59 

1


There are 10 numbers, 70, 70, 80, 80, 80,…100. If each of the smallest

MathRevolution 
2 
14 Jan 2016, 18:53 

8


Set A and Set B each contain three whole numbers ranging from 1 to 10.

Bunuel 
7 
22 May 2017, 08:39 

7


A number of eggs dyed various colors were hidden for an egg hunt. How

Bunuel 
3 
18 Nov 2014, 08:10 

6


Each of the eggs in a bowl is dyed red, or green, or blue. If one egg

Lolaergasheva 
6 
28 Oct 2016, 20:34 



