Events & Promotions
|
|
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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Apr 2711:00 AM EDT
-12:00 PM EDT
Prefer video-based learning? The Target Test Prep OnDemand course is a one-of-a-kind video masterclass featuring 400 hours of lecture-style teaching by Scott Woodbury-Stewart, founder of Target Test Prep and one of the most accomplished GMAT instructors
Apr 2808:00 AM PDT
-11:00 AM PDT
Whether you are just beginning your MBA journey or fine-tuning your path to a 700+ score, GMAT Day is designed to give you a competitive edge.
16 Aug 2016, 06:10
Kudos
Bookmarks
C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
35%
(medium)
Question Stats:
69% (01:36) correct
31%
(01:29)
wrong
based on 325
sessions
History
Date
Time
Result
Not Attempted Yet
Closing prices for a certain stock were recorded each day for a week in the table above. If the monthly average (arithmetic mean) was 18.43 and the standard deviation was 0.27, how many days during this week did the closing price fall within two standard deviations from the average?
A. 1
B. 2
C. 3
D. 4
E. 5
Attachment:
2016-08-16_1709.png [ 11.51 KiB | Viewed 9190 times ]
Updated on: 22 Jan 2020, 17:23
Originally posted by BrentGMATPrepNow on 16 Aug 2016, 07:26.
Last edited by BrentGMATPrepNow on 22 Jan 2020, 17:23, edited 1 time in total.
Last edited by BrentGMATPrepNow on 22 Jan 2020, 17:23, edited 1 time in total.
Kudos
Bookmarks
Bunuel
A little extra background on standard deviations above and below the mean
If, for example, a set has a standard deviation of 4, then:
1 standard deviation = 4
2 standard deviations = 8
3 standard deviations = 12
1.5 standard deviations = 6
0.25 standard deviations = 1
etc
So, if the mean of a set is 9, and the standard deviation is 4, then:
2 standard deviations ABOVE the mean = 17 [since 9 + 2(4) = 17]
1.5 standard deviations BELOW the mean = 3 [since 9 - 1.5(4) = 3]
3 standard deviations ABOVE the mean = 21 [since 9 + 3(4) = 21]
etc.
-----------------------------
For this question, the mean is 18.43 and the standard deviation is 0.27
So, two standard deviations = (2)(0.27) = 0.54
So, two standard deviations BELOW the mean = 18.43 - 0.54 = 17.89
And two standard deviations ABOVE the mean = 18.43 + 0.54 = 18.97
So, the RANGE of acceptable values lies between 17.89 and 18.97
When we check the table, we see there are 3 values in this range
Answer:
General Discussion
Senthil1981
Joined: 23 Apr 2015
Last visit: 14 Oct 2021
Posts: 225
Own Kudos:
Given Kudos: 36
Location: United States
Concentration: General Management, International Business
Schools: Booth PT '19 Ross Weekend"19
WE:Engineering (Consulting)
16 Aug 2016, 06:59
Kudos
Bookmarks
Bunuel
The range that's 2 SD away would be 18.43 - 2*0.27 = 17.89 to 18.43 + 2*0.27=18.97
Only 2 days (Thursday and Friday), stocks are out of range.
Answer is 3 C)
