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

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

Standard Deviation

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Junior | Next Rank: 30 Posts
Posts: 29
Joined: Tue Dec 23, 2008 11:42 am
Thanked: 1 times
by bburton11 » Fri Jun 12, 2009 6:47 am
For a certain examination, a score of 58 was 2 standard deviation below the mean, and a score of 98 was 3 standard deviation above the mean. What was the mean score for the examination?

74

*I don’t know why standard deviation is such a problem for me
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
Legendary Member
Posts: 1035
Joined: Wed Aug 27, 2008 10:56 pmFollowed by: 1 member
Thanked: 104 times

by scoobydooby » Fri Jun 12, 2009 6:53 am
98=M+3SD..............1
58=M-2SD...............2

subtracting 2 from 1 we get 40=5SD=> SD=8

replacing in either 1 or 2 we get M=74
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 472
Joined: Sun Mar 29, 2009 6:54 pm
Thanked: 56 times

by ssmiles08 » Fri Jun 12, 2009 7:17 am
you know another helpful way is just draw out a small diagram:

58 (2)---(1)---(0)----(1)----(2)----(3) 98

total distance is 5 std. deviations

so its 98 - 58 = 40

40/5 = 8.

each st. dev is 8 units apart. We also know (0) is the mean. so 58 + 16 = 74
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 19
Joined: Fri May 23, 2008 10:32 am
Thanked: 1 times

by gauravkhare » Fri Jun 12, 2009 11:36 am
you know another helpful way is just draw out a small diagram:

58 (2)---(1)---(0)----(1)----(2)----(3) 98

total distance is 5 std. deviations

so its 98 - 58 = 40

40/5 = 8.

each st. dev is 8 units apart. We also know (0) is the mean. so 58 + 16 = 74

GOOD ONE!!!!
gaurav
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1