Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 350,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Each week we'll be posting several questions from The Official Guide for GMAT® Review, 13th Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution.

We'll be glad if you participate in development of this project: 1. Please provide your solutions to the questions; 2. Please vote for the best solutions by pressing Kudos button; 3. Please vote for the questions themselves by pressing Kudos button; 4. Please share your views on difficulty level of the questions, so that we have most precise evaluation.

Re: Is the standard deviation of the set of measurements x1, x2, [#permalink]
25 Jun 2012, 02:02

1

This post received KUDOS

Expert's post

1

This post was BOOKMARKED

SOLUTION

Is the standard deviation of the set of measurements x1, x2, x3, x4, ..., x20 less than 3 ?

CALCULATING STANDARD DEVIATION OF A SET {x1, x2, ... xn}: 1. Find the mean, \(m\), of the values. 2. For each value \(x_i\) calculate its deviation (\(m-x_i\)) from the mean. 3. Calculate the squares of these deviations. 4. Find the mean of the squared deviations. This quantity is the variance. 5. Take the square root of the variance. The quantity is th SD.

Expressed by formula: \(standard \ deviation= \sqrt{variance} = \sqrt{\frac{\sum(m-x_i)^2}{N}}\).

(1) The variance for the set of measurements is 4. The variance is just the square of the standard deviation, so if \(variance=4\) then \(SD=\sqrt{4}=2\). Sufficient.

(2) For each measurement, the difference between the mean and that measurement is 2. So, we have that \(m-x_i=2\), since N=20 then we know everything to calculate the standard deviation. Sufficient.

Re: Is the standard deviation of the set of measurements x1, x2, [#permalink]
29 Jun 2012, 03:28

Expert's post

1

This post was BOOKMARKED

SOLUTION

Is the standard deviation of the set of measurements x1, x2, x3, x4, ..., x20 less than 3 ?

CALCULATING STANDARD DEVIATION OF A SET {x1, x2, ... xn}: 1. Find the mean, \(m\), of the values. 2. For each value \(x_i\) calculate its deviation (\(m-x_i\)) from the mean. 3. Calculate the squares of these deviations. 4. Find the mean of the squared deviations. This quantity is the variance. 5. Take the square root of the variance. The quantity is th SD.

Expressed by formula: \(standard \ deviation= \sqrt{variance} = \sqrt{\frac{\sum(m-x_i)^2}{N}}\).

(1) The variance for the set of measurements is 4. The variance is just the square of the standard deviation, so if \(variance=4\) then \(SD=\sqrt{4}=2\). Sufficient.

(2) For each measurement, the difference between the mean and that measurement is 2. So, we have that \(m-x_i=2\), since N=20 then we know everything to calculate the standard deviation. Sufficient.

Re: Is the standard deviation of the set of measurements x1, x2, [#permalink]
29 Jun 2012, 03:55

Is the standard deviation of the set of measurements x1, x2, x3, x4, ..., x20 less than 3 ?

(1) The variance for the set of measurements is 4. (2) For each measurement, the difference between the mean and that measurement is 2.

1 Statement:

s.deviation = sqrt(variance) = > thus, the std is 2. Sufficient;

2 Statement:

The standard deviation cannot be greater than the difference of observation and the mean of the population, (take min and max of the population compare to mean). Thus, we can safely assume that the std is less than 3. Sufficient.

Re: Is the standard deviation of the set of measurements x1, x2, [#permalink]
19 Sep 2012, 22:23

Bunuel wrote:

SOLUTION

Is the standard deviation of the set of measurements x1, x2, x3, x4, ..., x20 less than 3 ?

CALCULATING STANDARD DEVIATION OF A SET {x1, x2, ... xn}: 1. Find the mean, \(m\), of the values. 2. For each value \(x_i\) calculate its deviation (\(m-x_i\)) from the mean. 3. Calculate the squares of these deviations. 4. Find the mean of the squared deviations. This quantity is the variance. 5. Take the square root of the variance. The quantity is th SD.

Expressed by formula: \(standard \ deviation= \sqrt{variance} = \sqrt{\frac{\sum(m-x_i)^2}{N}}\).

(1) The variance for the set of measurements is 4. The variance is just the square of the standard deviation, so if \(variance=4\) then \(SD=\sqrt{4}=2\). Sufficient

(2) For each measurement, the difference between the mean and that measurement is 2. So, we have that \(m-x_i=2\), since N=20 then we know everything to calculate the standard deviation. Sufficient.

Re: Is the standard deviation of the set of measurements x1, x2, [#permalink]
19 Jun 2014, 16:37

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________

Type of Visa: You will be applying for a Non-Immigrant F-1 (Student) US Visa. Applying for a Visa: Create an account on: https://cgifederal.secure.force.com/?language=Englishcountry=India Complete...