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 500,000 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:

For what percent of those tested for a certain infection [#permalink]

Show Tags

06 Jan 2013, 02:59

1

This post received KUDOS

10

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

35% (medium)

Question Stats:

66% (01:14) correct
34% (01:17) wrong based on 384 sessions

HideShow timer Statistics

For what percent of those tested for a certain infection was the test accurate; that is, positive for those who had the infection and negative for those who did not have the infection?

(1) Of those who tested positive for the infection,1/8 did not have the infection. (2) Of those tested for the infection, 90 percent tested negative.

Re: For what percent of those tested for a certain infection [#permalink]

Show Tags

06 Jan 2013, 03:19

1

This post received KUDOS

2

This post was BOOKMARKED

gmatbull wrote:

For what percent of those tested for a certain infection was the test accurate; that is, positive for those who had the infection and negative for those who did not have the infection?

(1) Of those who tested positive for the infection,1/8 did not have the infection. (2) Of those tested for the infection, 90 percent tested negative.

For my simplicity I took a smart number as 80. In the attached diagram, we are supposed to find the red area.

We don't have sufficient information to find the red area. +1E

Re: For what percent of those tested for a certain infection [#permalink]

Show Tags

09 Jan 2013, 10:25

2

This post received KUDOS

gmatbull wrote:

For what percent of those tested for a certain infection was the test accurate; that is, positive for those who had the infection and negative for those who did not have the infection?

(1) Of those who tested positive for the infection,1/8 did not have the infection. (2) Of those tested for the infection, 90 percent tested negative.

I approached as shown below:

The question asks for %age of accuracy. 1. This option is doesn't give complete information. It says 1/8th did not have infection, but OUT OF HOW MANY POSITIVES. And another detail that is missing here is about accuracy of those who are tested negative. so, INSUFFICIENT.

2. 90% are negative, but what is the accuracy of those tested negative/positive? This information is not present. so, INSUFFICIENT.

(1+2) for positives accuracy is 1/8th of 10% (100 minus 90). For negatives, we dont know accuracy. so, INSUFFICIENT.

Re: For what percent of those tested for a certain infection [#permalink]

Show Tags

18 Jan 2013, 12:17

6

This post received KUDOS

3

This post was BOOKMARKED

fozzzy wrote:

isn't this question asking for 2 variables? I got the answer E

Attachment:

Infection tests.jpg [ 122.08 KiB | Viewed 6590 times ]

I think this problem goes beyond 2 variables. You can use the overlapping sets table, as there can be 4 possibilities for patient to be infected/not-infected: Tests are Positive & Accurate -> Patient is infected Tests are Positive & Inaccurate -> Patient is NOT infected Tests are Negative & Accurate -> Patient is NOT infected Tests are Negative & Inaccurate -> Patient is infected

Our objective is to identify the value of cell marked in yellow (i.e. Accurate tests) hence find its ratio to TOTAL tests (i.e. % Accuracy)

(1) Of those who tested positive for the infection,1/8 did not have the infection. INSUFFICIENT: Refer to the diagram, this gives no info to derive the value for yellow cell (i.e. Accurate tests) (2) Of those tested for the infection, 90 percent tested negative. INSUFFICIENT: Refer to the diagram, this gives no info to derive the value for yellow cell (i.e. Accurate tests)

Combining (1) & (2) INSUFFICIENT: Even after combining the statements are INSUFFICIENT to derive the value for yellow cell (i.e. Accurate tests)

Re: For what percent of those tested for a certain infection [#permalink]

Show Tags

29 Jan 2014, 16:14

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.
_________________

Re: For what percent of those tested for a certain infection [#permalink]

Show Tags

20 Apr 2015, 21:13

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.
_________________

Re: For what percent of those tested for a certain infection [#permalink]

Show Tags

15 May 2015, 02:28

think simple.

we need to know the fraction of nagative result and the fraction of positive result. we also need to know for each fraction, how many percent of each fraction is fake.

that is all
_________________

visit my facebook to help me. on facebook, my name is: thang thang thang

Re: For what percent of those tested for a certain infection [#permalink]

Show Tags

23 Feb 2017, 08:06

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.
_________________

Re: For what percent of those tested for a certain infection [#permalink]

Show Tags

01 Aug 2017, 07:00

Bunuel I understood the explanations but since from statement 1 the fraction for not having the infection of those tested positive is 1/8 then those tested positive and the result being accurate is 7/8 , So since the positive and accurate results are 7/8 then can we not consider 1/8 to be the fraction for negative and accurate.Thanks in advance

Re: For what percent of those tested for a certain infection [#permalink]

Show Tags

14 Aug 2017, 09:57

(1) Of those who tested positive for the infection,1/8 did not have the infection: Insufficient data. No numerical/ratio info is given about those who tested positive. (2) Of those tested for the infection, 90 percent tested negative : 9/10 -ve & 1/10 +ve. No other information about the certainty is provided. hence insufficient.

1 & 2 together, 1/8 X 1/10 = 1/80 did not have but still tested +ve. 1/10-1/80 = 7/80 did have and tested positive. but no info is provided about those who tested negative. hence 1 & 2 together insufficient.

For what percent of those tested for a certain infection was the test accurate; that is, positive for those who had the infection and negative for those who did not have the infection?

(1) Of those who tested positive for the infection,1/8 did not have the infection. (2) Of those tested for the infection, 90 percent tested negative.

Statement One Alone:

Of those who tested positive for the infection,1/8 did not have the infection.

We can let the total people who tested positive for the infection = p; thus, (7/8)p tested positive and had the infection. However, since we know nothing about those who tested negative, we cannot determine an answer. Statement one alone is not sufficient to answer the question.

Statement Two Alone:

Of those tested for the infection, 90 percent tested negative.

Using the information in statement two, we know that 90 percent tested negative and 10 percent tested positive. However, we still do not have enough information to answer the question.

Statements One and Two Together:

Using both statements, we still do not have information about those who did not have the infection and tested negative; we cannot determine an answer.

Answer: E
_________________

Scott Woodbury-Stewart Founder and CEO

GMAT Quant Self-Study Course 500+ lessons 3000+ practice problems 800+ HD solutions

We’ve given one of our favorite features a boost! You can now manage your profile photo, or avatar , right on WordPress.com. This avatar, powered by a service...

Sometimes it’s the extra touches that make all the difference; on your website, that’s the photos and video that give your content life. You asked for streamlined access...

A lot has been written recently about the big five technology giants (Microsoft, Google, Amazon, Apple, and Facebook) that dominate the technology sector. There are fears about the...

Post today is short and sweet for my MBA batchmates! We survived Foundations term, and tomorrow's the start of our Term 1! I'm sharing my pre-MBA notes...