Last visit was: 23 Nov 2024, 18:15 It is currently 23 Nov 2024, 18:15

Close

GRE Prep 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
Your Progress

every week, we’ll send you an estimated GRE 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.

Close

Request Expert Reply

Confirm Cancel
Retired Moderator
Joined: 16 Apr 2020
Status:Founder & Quant Trainer
Affiliations: Prepster Education
Posts: 1546
Own Kudos [?]: 3224 [16]
Given Kudos: 172
Location: India
WE:Education (Education)
Send PM
Most Helpful Community Reply
Retired Moderator
Joined: 19 Nov 2020
Posts: 326
Own Kudos [?]: 373 [1]
Given Kudos: 64
GRE 1: Q160 V152
Send PM
General Discussion
Retired Moderator
Joined: 19 Nov 2020
Posts: 326
Own Kudos [?]: 373 [2]
Given Kudos: 64
GRE 1: Q160 V152
Send PM
Retired Moderator
Joined: 16 Apr 2020
Status:Founder & Quant Trainer
Affiliations: Prepster Education
Posts: 1546
Own Kudos [?]: 3224 [3]
Given Kudos: 172
Location: India
WE:Education (Education)
Send PM
A terrible disease sweeps around the world, luckily only affecting 1 [#permalink]
3
Explanation:

If a person has a positive report then, there is 99% of chance that he is actually positive
i.e. He will be the 1 out of those 10000 tested.

So, Probability = \(\frac{1}{10000}(0.99) = \frac{99}{1000000}\)

There is also a 1% chance that he was tested fake positive
i.e. He will be the 9999 out of those 10000

So, Probability = \(\frac{9999}{10000}(0.01) = \frac{9999}{1000000}\)

Thus required Probability = \(\frac{0.000099}{(0.000099 + 0.009999)} = \frac{0.000099}{0.010098} = 0.009803\)

Col. A: 0.009803
Col. B: 0.009803

Hence, option C
Manager
Manager
Joined: 18 Jan 2021
Posts: 81
Own Kudos [?]: 20 [0]
Given Kudos: 103
Send PM
Re: A terrible disease sweeps around the world, luckily only affecting 1 [#permalink]
KarunMendiratta wrote:
Explanation:

If a person has a positive report then, there is 99% of chance that he is actually positive
i.e. He will be the 1 out of those 10000 tested.

So, Probability = \(\frac{1}{10000}(0.99) = \frac{99}{1000000}\)

There is also a 1% chance that he was tested fake positive
i.e. He will be the 9999 out of those 10000

So, Probability = \(\frac{9999}{10000}(0.01) = \frac{9999}{1000000}\)

Thus required Probability = \(\frac{0.000099}{(0.000099 + 0.009999)} = \frac{0.000099}{0.010098} = 0.009803\)

Col. A: 0.009803
Col. B: 0.009803

Hence, option C

Could you please help me understand if we already considered true positive then why do we need to consider false positive?
Retired Moderator
Joined: 16 Apr 2020
Status:Founder & Quant Trainer
Affiliations: Prepster Education
Posts: 1546
Own Kudos [?]: 3224 [1]
Given Kudos: 172
Location: India
WE:Education (Education)
Send PM
Re: A terrible disease sweeps around the world, luckily only affecting 1 [#permalink]
1
Bookmarks
koala wrote:
KarunMendiratta wrote:
Explanation:

If a person has a positive report then, there is 99% of chance that he is actually positive
i.e. He will be the 1 out of those 10000 tested.

So, Probability = \(\frac{1}{10000}(0.99) = \frac{99}{1000000}\)

There is also a 1% chance that he was tested fake positive
i.e. He will be the 9999 out of those 10000

So, Probability = \(\frac{9999}{10000}(0.01) = \frac{9999}{1000000}\)

Thus required Probability = \(\frac{0.000099}{(0.000099 + 0.009999)} = \frac{0.000099}{0.010098} = 0.009803\)

Col. A: 0.009803
Col. B: 0.009803

Hence, option C

Could you please help me understand if we already considered true positive then why do we need to consider false positive?


Because the total outcomes would be all possibilities of getting a positive result i.e. 99% positive (Actual) + 1% positive (Fake)
User avatar
GRE Prep Club Legend
GRE Prep Club Legend
Joined: 07 Jan 2021
Posts: 5043
Own Kudos [?]: 74 [0]
Given Kudos: 0
Send PM
Re: A terrible disease sweeps around the world, luckily only affecting 1 [#permalink]
Hello from the GRE Prep Club BumpBot!

Thanks to another GRE Prep 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.
Prep Club for GRE Bot
Re: A terrible disease sweeps around the world, luckily only affecting 1 [#permalink]
Moderators:
GRE Instructor
84 posts
GRE Forum Moderator
37 posts
Moderator
1111 posts
GRE Instructor
234 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne