GMAT Question of the Day: Daily via email | Daily via Instagram New to GMAT Club? Watch this Video

 It is currently 26 May 2020, 21:04 ### 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

#### Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  # The mean score in a certain test is 80. If the test scores have a norm Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

### Hide Tags

Manager  Joined: 08 Jan 2009
Posts: 202
The mean score in a certain test is 80. If the test scores have a norm  [#permalink]

### Show Tags

2
9 00:00

Difficulty:   55% (hard)

Question Stats: 53% (01:31) correct 47% (01:23) wrong based on 103 sessions

### HideShow timer Statistics

The mean score in a certain test is 80. If the test scores have a normal distribution and the standarad distribution is 7, what percent of examinees score between 66 and 94?

A) 50%
B) 68%
C) 82%
D) 96%
E) 98%
Manager  Joined: 08 Jan 2009
Posts: 202
Re: The mean score in a certain test is 80. If the test scores have a norm  [#permalink]

### Show Tags

Thank you.

I read through the description now i get it.

The percentages 34: 14 : 2 corresponds to the 1st , 2nd and 3rd standard deviation on each side of the mean.

So our case 66 and 94 are two std deviation away from the mean.

14 + 34 + 34 + 14 = 96%
Manager  Joined: 25 Jun 2009
Posts: 211
Re: The mean score in a certain test is 80. If the test scores have a norm  [#permalink]

### Show Tags

tkarthi4u wrote:
Thank you.

I read through the description now i get it.

The percentages 34: 14 : 2 corresponds to the 1st , 2nd and 3rd standard deviation on each side of the mean.

So our case 66 and 94 are two std deviation away from the mean.

14 + 34 + 34 + 14 = 96%

Hi,
Can you please explain how did you get that?

Thanks
Manager  Joined: 18 Jul 2009
Posts: 123
Location: India
Schools: South Asian B-schools
Re: The mean score in a certain test is 80. If the test scores have a norm  [#permalink]

### Show Tags

2
1
Normal distribution says

1 sigma = 68% (34% on either side) population
2 sigma = 96% (14% on either side) population so 68% +14%x 2=96%
3 sigma = 99.99% (2% on either side) population so 96% + 2% x 2 ~ 99.99 %
Manager  Joined: 10 Jul 2009
Posts: 83
Location: Ukraine, Kyiv
Re: The mean score in a certain test is 80. If the test scores have a norm  [#permalink]

### Show Tags

Try wikipedia to make it clear.

http://en.wikipedia.org/wiki/Normal_distribution
Manager  Joined: 27 Oct 2008
Posts: 128
Re: The mean score in a certain test is 80. If the test scores have a norm  [#permalink]

### Show Tags

The mean score in a certain test is 80. If the test scores have a normal distribution and the standarad distribution is 7, what percent of examinees score between 66 and 94?

A) 50%
B) 68%
C)82%
D)96%
E)98%

Soln: Here mean = 80
and standard deviation sig = 7
Since for a range of scores from 66 to 94, the scores vary between 2 * sig about mean
that is from -2 * sig to +2 * sig
for this range with normal distribution the percent of examinees is
= 13.6 + 34.1 + 34.1 + 13.6
= 95.4
Approximately 96%
Ans is D
Director  Status: There is always something new !!
Affiliations: PMI,QAI Global,eXampleCG
Joined: 08 May 2009
Posts: 723
Re: The mean score in a certain test is 80. If the test scores have a norm  [#permalink]

### Show Tags

interesting concept.

73 - 80 and 80-87 = 1 sigma = 34*2

66-73 and 87- 94 = 2 sigma = 14 * 2

total 96%
Manager  B
Joined: 20 Apr 2014
Posts: 87
Re: The mean score in a certain test is 80. If the test scores have a norm  [#permalink]

### Show Tags

i need more explanation from experts please. will I see this type of Qs in Gmat Test ?
Manager  Joined: 23 Sep 2015
Posts: 79
Concentration: General Management, Finance
GMAT 1: 680 Q46 V38
GMAT 2: 690 Q47 V38
GPA: 3.5
Re: The mean score in a certain test is 80. If the test scores have a norm  [#permalink]

### Show Tags

1
This question is just testing standard knowledge of a normal distribution graph.

The mean=80, mean 50% of the data falls above and below this point,

When we consider 1 standard deviation on either side of it, we are cutting the data points of interest down to 34% on each side, or 68% between them

As for the question we are being asked about the range +/- 2 SD from the mean. This tests us just knowing that this represents 96% of the data of the data points, or 48% on either side of the mean.

Hope this helps someone
Board of Directors P
Joined: 17 Jul 2014
Posts: 2435
Location: United States (IL)
Concentration: Finance, Economics
GMAT 1: 650 Q49 V30 GPA: 3.92
WE: General Management (Transportation)
Re: The mean score in a certain test is 80. If the test scores have a norm  [#permalink]

### Show Tags

normal distribution represents the bell curve, in which 50% is above mean, and 50% below mean
34% lies within 1 standard deviation or mean+SD and mean-SD
mean+-SD is 73 and 87.
68% of people have scores between 73 and 87
now, aprox. 14% is between (mean+2SD)-(Mean+SD), this is the same for mean minus 2 SD.
Mean+2SD=94
Mean-2SD=66

ok, so in total, we have 68% + 28 = aprox. 98%. Re: The mean score in a certain test is 80. If the test scores have a norm   [#permalink] 28 Nov 2015, 09:31

# The mean score in a certain test is 80. If the test scores have a norm Question banks Downloads My Bookmarks Reviews Important topics  