It is currently 14 Dec 2017, 05:34

# Decision(s) Day!:

CHAT Rooms | Wharton R1 | Stanford R1 | Tuck R1 | Ross R1 | Haas R1

### GMAT Club Daily Prep

#### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# For what percent of those tested for a certain infection was

Author Message
TAGS:

### Hide Tags

Manager
Joined: 23 Mar 2008
Posts: 216

Kudos [?]: 207 [0], given: 0

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

### Show Tags

01 May 2008, 20:30
3
This post was
BOOKMARKED
00:00

Difficulty:

35% (medium)

Question Stats:

72% (00:57) correct 28% (01:00) wrong based on 146 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.

OPEN DISCUSSION OF THIS QUESTION IS HERE: for-what-percent-of-those-tested-for-a-certain-infection-145310.html
[Reveal] Spoiler: OA

Kudos [?]: 207 [0], given: 0

Intern
Joined: 28 Apr 2008
Posts: 15

Kudos [?]: 1 [0], given: 0

### Show Tags

01 May 2008, 20:44
E, because we still don't know the percent of inaccuracy for the negative group.

Kudos [?]: 1 [0], given: 0

Manager
Joined: 06 Feb 2008
Posts: 84

Kudos [?]: 26 [0], given: 0

### Show Tags

01 May 2008, 21:36
Should we assume negative tests are not 100% accurate since question does not say so anywhere explicitly...!!!

Kudos [?]: 26 [0], given: 0

SVP
Joined: 28 Dec 2005
Posts: 1543

Kudos [?]: 189 [0], given: 2

### Show Tags

02 May 2008, 03:46
C, but not sure. I think its c because we know how many people did not have it from stat 1, and from stat 2 we know how many people the test said did not have it.

Kudos [?]: 189 [0], given: 2

CEO
Joined: 29 Mar 2007
Posts: 2553

Kudos [?]: 537 [1], given: 0

### Show Tags

02 May 2008, 04:55
1
KUDOS
puma 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.

Z--> .9z test negative so .1z test positive.

1/80z+ 7/80z =.1z

The answer should be E b/c we know nothing about the 90% who tested negative.

Kudos [?]: 537 [1], given: 0

Current Student
Joined: 06 Sep 2013
Posts: 1965

Kudos [?]: 759 [1], given: 355

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

### Show Tags

17 Oct 2013, 08:03
1
KUDOS
puma 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.

Agree, and I think this problem is best solved with a Double-Matrix

Just use Positive/Negative and Tested Positive/Tested Negative for each axis.
Then you will see that we are actually lacking the ones who tested negative.

Try it and let me know
Hope it helps

Cheers
J

Kudos [?]: 759 [1], given: 355

Math Expert
Joined: 02 Sep 2009
Posts: 42606

Kudos [?]: 135614 [0], given: 12705

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

### Show Tags

17 Oct 2013, 08:07
OPEN DISCUSSION OF THIS QUESTION IS HERE: for-what-percent-of-those-tested-for-a-certain-infection-145310.html
_________________

Kudos [?]: 135614 [0], given: 12705

Re: For what percent of those tested for a certain infection was   [#permalink] 17 Oct 2013, 08:07
Display posts from previous: Sort by

# For what percent of those tested for a certain infection was

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.