BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

standard deviation

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |
User avatar
Legendary Member
Posts: 1309
Joined: Mon Apr 04, 2011 5:34 am
Location: India
Thanked: 310 times
Followed by:123 members
GMAT Score:750

by cans » Fri Sep 23, 2011 7:20 am
mean=20, sd=3. 2.5sd = 2.5*3 = 7.5
thus more than 2.5sd from mean = 20 +- 7.5
more than 27.5 or less than 12.5
IMO A
If my post helped you- let me know by pushing the thanks button ;)

Contact me about long distance tutoring!
[email protected]

Cans!!
Top
User avatar
Legendary Member
Posts: 504
Joined: Tue Apr 19, 2011 1:40 pm
Thanked: 114 times
Followed by:11 members

by knight247 » Fri Sep 23, 2011 7:20 am
20 is the mean of all the numbers in that sample of data. Lets draw a number line for the number 20.

|-----------20-----------|

Standard deviation of 3 means that all the values in that sample vary between the range (20-3) to (20+3) i.e. between 17 to 23.

|-------17----20----23-------|

Now, if standard deviation is 3 then 2.5 times the standard deviation is 7.5. So, we need to find which value lies outside of 7.5 from the mean i.e. which values lie outside of the range 20+7.5 to 20-7.5. Can be written as 12.5 to 27.5 The only one that lies outside this range from among the answer choices is 12 hence A
Top
Post new topic Post Reply
• Page 1 of 1