Live GMAT classes with Target Test Prep start Nov 21 and Nov 22. First class free.

See classes
Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

Newsweek Readers’ Choice Awards 2026 winner: Target Test Prep, #1 Test Prep

Target Test Prep was voted #1 Best Test Prep in the 2026 Newsweek Readers’ Choice™ Awards.

★★★★★5.0563 reviews
GMATLiveTeachStarts Nov 22
Josh Braslow, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Josh Braslow, 20+ years in test prep

Nov 22 · Josh Braslow
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemandStart anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

EXECUTIVE ASSESSMENT

with

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemandStart anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 563 reviewsTarget Test Prep

Standard deviation

Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 320
Joined: Sun Jan 13, 2008 10:00 pm
Thanked: 10 times
by ildude02 » Sun Sep 21, 2008 8:04 pm
My approach was, I got mean of 100 and then SD was 22.4 or 22. So, 1SD less than 100 was 78 and the question I thought was asking for how many times are more then 78, obvisouly I went wrong somewhere. Appreciate anyones response.
You do not have the required permissions to view the files attached to this post.
Top
Join the discussion
Source: — Problem Solving |
Senior | Next Rank: 100 Posts
Posts: 85
Joined: Wed Mar 26, 2008 9:49 pm
Location: NJ, USA
Thanked: 1 times

by csandeepreddy » Sun Sep 21, 2008 8:26 pm
The question is asking for more than 1SD below the mean.

# below 78 from the sample set.

Is the answer 2?
Top
Join the discussion
Junior | Next Rank: 30 Posts
Posts: 17
Joined: Wed Aug 27, 2008 11:14 pm

Re: Standard deviation

by justpal » Sun Sep 21, 2008 8:52 pm
The mean for the list of running times is
1000 / 10 = 100

SD = 22.4

Ques asks for how many running times are more that one SD below mean
that is 100-22.4 = 77.6

and we got 70 and 75 less than 77.6

Answer is TWO (B)
Top
Join the discussion
User avatar
Legendary Member
Posts: 871
Joined: Wed Aug 13, 2008 7:48 am
Thanked: 48 times

Re: Standard deviation

by stop@800 » Mon Sep 22, 2008 7:50 am
ildude02 wrote:My approach was, I got mean of 100 and then SD was 22.4 or 22. So, 1SD less than 100 was 78 and the question I thought was asking for how many times are more then 78,
we need to find how many nos are below 17
its 2 ie 70 and 75
ildude02 wrote:
obvisouly I went wrong somewhere. Appreciate anyones response.
[/quote]
Top
Join the discussion