The list shown consist of the times, in seconds, that it took each of 10 school children to run a distance of 400 meters

Expert replies

Previous Topic Next Topic

Gmat_mission: Legendary Member; Posts: 1622; Joined: Thu Mar 01, 2018 7:22 amFollowed by: 2 members

by Gmat_mission » Thu Sep 24, 2020 2:29 am

Timer

00:00

Your answer

Difficulty–

right wrong

Pick an answer to see how members did

70, 75, 80, 85, 90, 105, 105, 130, 130, 130

The list shown consist of the times, in seconds, that it took each of 10 school children to run a distance of 400 meters. If the SD of ten running times is 22.4 seconds, rounded to the nearest tenth of second, how many of the 10 running times are more than one SD below the mean of the 10 running times?

A. one
B. two
C. three
D. four
E. five

Answer: B

Source: GMAT Prep

Source: Beat The GMAT — Problem Solving | Thu Sep 24, 2020 2:29 am

GMAT/MBA Expert

Scott@TargetTestPrep: GMAT Instructor; Posts: 8246; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

Re: The list shown consist of the times, in seconds, that it took each of 10 school children to run a distance of 400 me

by Scott@TargetTestPrep » Thu Oct 01, 2020 10:00 am

Gmat_mission wrote: ↑
Thu Sep 24, 2020 2:29 am
70, 75, 80, 85, 90, 105, 105, 130, 130, 130

The list shown consist of the times, in seconds, that it took each of 10 school children to run a distance of 400 meters. If the SD of ten running times is 22.4 seconds, rounded to the nearest tenth of second, how many of the 10 running times are more than one SD below the mean of the 10 running times?

A. one
B. two
C. three
D. four
E. five

Answer: B

Source: GMAT Prep

Solution:

The average (mean) is:

(70 + 75 + 80 + 85 + 90 + 105 + 105 + 130 +130 +130)/10 = 1000/10 = 100

Thus, 1 standard deviation below the mean is 100 - 22.4 = 77.6, so there are 2 running times that are more than 1 standard deviation below the mean.

Answer: B

Scott Woodbury-Stewart
Founder and CEO
[email protected]

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

Featured schoolRound 2 closes Jan 7, 2027 54 days left

Chicago Booth

Since 1982, 10 Booth faculty members have received the Nobel Prize in Economic Sciences, more than any other business school.

#3
U.S. News rank: $175,000
Median base salary: 670
Average GMAT Focus: 635
Students in the class

Apply to Booth Visit chicagobooth.edu See the full profile

Photo: Warren LeMay, CC BY-SA 2.0

GMAT Course Reviews

563 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (563 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review