It is currently 23 Oct 2017, 12:45

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

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

A scientist recorded the number of eggs in each of 10 birds'

Author Message
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 41913

Kudos [?]: 129493 [0], given: 12201

A scientist recorded the number of eggs in each of 10 birds' [#permalink]

Show Tags

11 Sep 2012, 04:50
Expert's post
17
This post was
BOOKMARKED
00:00

Difficulty:

5% (low)

Question Stats:

76% (00:35) correct 24% (00:40) wrong based on 1251 sessions

HideShow timer Statistics

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
[Reveal] Spoiler: OA

_________________

Kudos [?]: 129493 [0], given: 12201

Math Expert
Joined: 02 Sep 2009
Posts: 41913

Kudos [?]: 129493 [2], given: 12201

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]

Show Tags

11 Sep 2012, 04:50
2
KUDOS
Expert's post
9
This post was
BOOKMARKED
SOLUTION

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?

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.

_________________

Kudos [?]: 129493 [2], given: 12201

Intern
Joined: 12 Jun 2012
Posts: 41

Kudos [?]: 39 [2], given: 28

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]

Show Tags

11 Sep 2012, 08:13
2
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(x-Mean)^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,

_________________

Kudos [?]: 39 [2], given: 28

Senior Manager
Joined: 15 Jun 2010
Posts: 358

Kudos [?]: 453 [2], given: 50

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
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"

_________________

Regards
SD
-----------------------------
Press Kudos if you like my post.
Debrief 610-540-580-710(Long Journey): http://gmatclub.com/forum/from-600-540-580-710-finally-achieved-in-4th-attempt-142456.html

Kudos [?]: 453 [2], given: 50

Senior Manager
Joined: 24 Aug 2009
Posts: 498

Kudos [?]: 841 [1], given: 276

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
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.

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

Kudos [?]: 841 [1], given: 276

Manager
Joined: 18 Oct 2011
Posts: 90

Kudos [?]: 91 [0], given: 0

Location: United States
Concentration: Entrepreneurship, Marketing
GMAT Date: 01-30-2013
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.

Kudos [?]: 91 [0], given: 0

Manager
Joined: 07 Apr 2014
Posts: 138

Kudos [?]: 31 [0], given: 81

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

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

Kudos [?]: 31 [0], given: 81

Senior Manager
Joined: 20 Aug 2015
Posts: 396

Kudos [?]: 337 [0], given: 10

Location: India
GMAT 1: 760 Q50 V44
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 SD

Required: 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
INSUFFICIENT

Statement 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)
SUFFICIENT

Option B
_________________

Reach out to us at bondwithus@gmatify.com

Kudos [?]: 337 [0], given: 10

Target Test Prep Representative
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 1545

Kudos [?]: 841 [0], given: 5

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]

Show Tags

25 Aug 2016, 16:01
Expert's post
1
This post was
BOOKMARKED
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.

_________________

Jeffery Miller

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Kudos [?]: 841 [0], given: 5

SVP
Joined: 12 Sep 2015
Posts: 1798

Kudos [?]: 2476 [0], given: 357

Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]

Show Tags

03 Aug 2017, 13:30
Expert's post
Top Contributor
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.

Target question: What was the 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.
There are several scenarios that satisfy statement 1. Here are two:
Case a: the numbers are {4, 4, 4, 4, 4, 4, 4, 4, 4, 4, }, in which case the standard deviation is zero
Case b: the numbers are the numbers are {0, 0, 4, 4, 4, 4, 4, 4, 4, 4, 8, 8}, in which case the standard deviation is NOT zero
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: Each of the 10 nests contained the same number of eggs.
In other words, all 10 data values are the same, which means there is NO deviation among the values.
So, the standard deviation is zero
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

[Reveal] Spoiler:
B

RELATED VIDEO

_________________

Brent Hanneson – Founder of gmatprepnow.com

Kudos [?]: 2476 [0], given: 357

Senior Manager
Joined: 29 Jun 2017
Posts: 347

Kudos [?]: 67 [0], given: 64

WE: Engineering (Transportation)
Re: A scientist recorded the number of eggs in each of 10 birds' [#permalink]

Show Tags

17 Aug 2017, 02:21

1) mean is 4 , we dont know the number of eggs hence insufficient A,D gone
2) All contain equal number of eggs, lets say X X X X X X X X X X. mean is X and SD will be Zero = 0 therefore ans is B
_________________

Give Kudos for correct answer and/or if you like the solution.

Kudos [?]: 67 [0], given: 64

Re: A scientist recorded the number of eggs in each of 10 birds'   [#permalink] 17 Aug 2017, 02:21
Display posts from previous: Sort by