• Economist Test Prep
    Free Trial & Practice Exam
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    Economist Test Prep
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • Kaplan Test Prep
    Free Practice Test & Review
    How would you score if you took the GMAT

    Available with Beat the GMAT members only code

    MORE DETAILS
    Kaplan Test Prep
  • Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh
  • examPAL
    Most awarded test prep in the world
    Now free for 30 days

    Available with Beat the GMAT members only code

    MORE DETAILS
    examPAL
  • Varsity Tutors
    Award-winning private GMAT tutoring
    Register now and save up to $200

    Available with Beat the GMAT members only code

    MORE DETAILS
    Varsity Tutors
  • Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

    MORE DETAILS
    Veritas Prep
  • PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT
  • Target Test Prep
    5-Day Free Trial
    5-day free, full-access trial TTP Quant

    Available with Beat the GMAT members only code

    MORE DETAILS
    Target Test Prep
  • e-gmat Exclusive Offer
    Get 300+ Practice Questions
    25 Video lessons and 6 Webinars for FREE

    Available with Beat the GMAT members only code

    MORE DETAILS
    e-gmat Exclusive Offer

Statistics

This topic has 3 expert replies and 0 member replies
Apoorva@5 Junior | Next Rank: 30 Posts Default Avatar
Joined
03 Jun 2016
Posted:
21 messages

Statistics

Post Fri Jul 01, 2016 11:40 pm
The residents of Town X participated in a survey to determine the no. of hours per week each resident spent watching TV. The distribution of the results of the survey had a mean of 21 hours and a standard deviation of 6 hours.The no. of hours that Pat,A resident of Town X,watched TV last week was between 1&2 standard deviation below mean. so, the no. of hours he watched TV last week is?

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

Matt@VeritasPrep GMAT Instructor
Joined
12 Sep 2012
Posted:
2640 messages
Followed by:
113 members
Upvotes:
625
Target GMAT Score:
V51
GMAT Score:
780
Post Sun Aug 06, 2017 10:47 pm
If the mean is 21 and the sd is 6, then

mean = 21
one sd below = 21 - 6 = 15
two sds below = 21 - 2*6 = 9

so the answer should be between 9 and 15.

  • +1 Upvote Post
  • Quote
  • Flag
Enroll in a Veritas Prep GMAT class completely for FREE. Wondering if a GMAT course is right for you? Attend the first class session of an actual GMAT course, either in-person or live online, and see for yourself why so many students choose to work with Veritas Prep. Find a class now!

GMAT/MBA Expert

Post Sat Jul 02, 2016 8:59 am
Hi Apoorva@5,

In the real world, Standard Deviation is based on a rather 'thick' math formula; thankfully, the GMAT will never ask you to use that formula or perform a standard deviation calculation that is all that complicated. SD is a rather rare subject on Test Day (you'll likely see it on just one question) and you'll be tested more on your general knowledge of the concept than on anything else.

In this particular prompt, we're given the mean (21 hours) and the SD (6 hours). We're asked for a value that is BETWEEN 1 and 2 SDs BELOW the mean. Since SD goes in both 'directions' from the mean, we would have the following results:

1 SD away would be (21-6) = 15 and (21+6) = 27
2 SDs away would be 21-12) = 9 and (21+12) = 33

Since we're specifically asked for BELOW the mean, we'd be looking for an answer that was between 9 and 15.

GMAT assassins aren't born, they're made,
Rich

_________________
Contact Rich at Rich.C@empowergmat.com

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

Post Sat Jul 02, 2016 5:47 am
When posting, please provide the ENTIRE question, including the answer choices.
Here's a link with a nice solution: http://www.beatthegmat.com/an-issue-regarding-a-standard-deviation-calculation-t275194.html

Also, here's a video that covers the necessary concepts/skills to answer this question: https://www.gmatprepnow.com/module/gmat-statistics/video/809

Cheers,
Brent

_________________
Brent Hanneson – Founder of GMATPrepNow.com
Use our video course along with Beat The GMAT's free 60-Day Study Guide

Check out the online reviews of our course
Come see all of our free resources

  • +1 Upvote Post
  • Quote
  • Flag
GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months!

Best Conversation Starters

1 lheiannie07 108 topics
2 Roland2rule 63 topics
3 ardz24 63 topics
4 LUANDATO 50 topics
5 AAPL 42 topics
See More Top Beat The GMAT Members...

Most Active Experts

1 image description GMATGuruNY

The Princeton Review Teacher

152 posts
2 image description Jeff@TargetTestPrep

Target Test Prep

106 posts
3 image description Rich.C@EMPOWERgma...

EMPOWERgmat

104 posts
4 image description Scott@TargetTestPrep

Target Test Prep

96 posts
5 image description Max@Math Revolution

Math Revolution

87 posts
See More Top Beat The GMAT Experts