• Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

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

    Available with Beat the GMAT members only code

    MORE DETAILS
    Economist Test Prep
  • The Princeton Review
    FREE GMAT Exam
    Know how you'd score today for $0

    Available with Beat the GMAT members only code

    MORE DETAILS
    The Princeton Review
  • 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
  • PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT
  • 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
  • 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

The monthly sales (in thousands of $) at a certain...

This topic has 1 expert reply and 0 member replies

The monthly sales (in thousands of $) at a certain...

Post Sun Nov 05, 2017 7:20 am
The monthly sales (in thousands of $) at a certain restaurant for the past two years are given in the chart below:

Last year: 9, 9.5, 10, 10, 11, 11, 11, 11, 11, 12.5, 13, 13.
This year: 9, X, 10, 10, 11, 11, 11, 11, 11, Y, 13, 13.

If the standard deviation of the monthly sales is greater this year than last year, which of the following are possible values for X and Y?

A) 9 and 12.5
B) 10 and 11
C) 10 and 12.5
D) 11 and 11
E) 11 and 12.5

The OA is A.

Please, can any expert explain this PS question for me? I have many difficulties to understand why that is the correct answer. Thanks.

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

Post Sun Nov 05, 2017 12:17 pm
Hi swerve,

Standard Deviation questions on the GMAT are never about calculating an actual Standard Deviation - they're about the CONCEPT behind SD (how "spread out" a group of numbers is). It's a relatively rare concept on Test Day - you'll probably see it just once.

In this question, we're given lots of data that we're essentially going to ignore. We're told to make this year's SD larger than last years, which means that we have to make this year's group of numbers "more spread out" than last year's group of numbers. Put simply, we're looking to replace X and Y with 2 numbers that are as "far apart" from one another as possible.

The answer pair with the largest spread is

Final Answer: A

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

_________________
Contact Rich at Rich.C@empowergmat.com

  • +1 Upvote Post
  • Quote
  • Flag

Top First Responders*

1 GMATGuruNY 70 first replies
2 Rich.C@EMPOWERgma... 42 first replies
3 Brent@GMATPrepNow 40 first replies
4 Jay@ManhattanReview 24 first replies
5 Terry@ThePrinceto... 10 first replies
* Only counts replies to topics started in last 30 days
See More Top Beat The GMAT Members

Most Active Experts

1 image description GMATGuruNY

The Princeton Review Teacher

133 posts
2 image description Scott@TargetTestPrep

Target Test Prep

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

EMPOWERgmat

111 posts
4 image description Jeff@TargetTestPrep

Target Test Prep

111 posts
5 image description Brent@GMATPrepNow

GMAT Prep Now Teacher

90 posts
See More Top Beat The GMAT Experts