[Last Call] Learn about multicloud storage options and how to improve your company's cloud strategy. Register Now

x
Solved

# Statistics

Posted on 2016-10-20
Medium Priority
69 Views
A clinic offers you a free test for a very rare, but hideous disease. The test they offer is very reliable. If you have the disease it has a 98% chance of giving a positive result, and if you don’t have the disease, it has only a 1% chance of giving a positive result. You decide to take the test, and find that you test positive. What is the probability that you have the disease?
0
[X]
###### Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

• Help others & share knowledge
• Earn cash & points
• 4
• 2

LVL 27

Expert Comment

ID: 41852368
Welcome to Experts Exchange.  I see this is your first question.

If this is a homework question (and it looks like it might be), you need to say so up front and explain how far you have gotten and/or what you are having trouble with.

In this case, it looks like there isn't enough information to solve the problem.  If you don't know how rare the disease is (the probability of a random person having it), you have no way to filter out false positive results.
0

LVL 27

Expert Comment

ID: 41852596
Assume the prevalence of the disease is one case per million people.
If one million people take the test, how many TRUE Positives will there be?
And how many FALSE Positives?
0

LVL 27

Expert Comment

ID: 41853200
"In this case, it looks like there isn't enough information to solve the problem."
There is enough info to answer.
You have to combine two known probabilities.
If home work, show what you have done so far
0

LVL 27

Assisted Solution

d-glitch earned 1000 total points (awarded by participants)
ID: 41854127
Without making some assumption about the meaning of very rare, you can not give a quantitative answer.

False positives will dominate until the disease prevalence exceeds 1% of the population.
0

LVL 27

Accepted Solution

aburr earned 1000 total points (awarded by participants)
ID: 41854789
"Without making some assumption about the meaning of very rare, you can not give a quantitative answer.

False positives will dominate until the disease prevalence exceeds 1% of the population. "

d-glitch is correct. I was making some "reasonable" assumptions. But there are even more difficulties. The problem is a standard one emphasizing the often overlooked difficulty of the false negatives. Here the distinction is not made clear. Is there only one test? if so we are missing 1% of the population, etc
-
False Positives and False Negatives - Math is Fun
www.mathsisfun.com/data/probability-false-negatives-positives.html
Maths Is Fun
False Positives and False Negatives. Test Says "Yes" ... or does it? When you have a test that can say "Yes" or "No" (such as a medical test), you have to think:.
0

LVL 27

Expert Comment

ID: 41881890
As clear an explanation as possible.
0

## Featured Post

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

The CRUD Functions CRUD, meaning "Create, Read, Update, Delete (http://en.wikipedia.org/wiki/Create,_read,_update_and_delete)" is a common term to data base developers.  It describes the essential functions of data base table maintenance.  This art…
This is a research brief on the potential colonization of humans on Mars.
Although Jacob Bernoulli (1654-1705) has been credited as the creator of "Binomial Distribution Table", Gottfried Leibniz (1646-1716) did his dissertation on the subject in 1666; Leibniz you may recall is the co-inventor of "Calculus" and beat Isaac…
I've attached the XLSM Excel spreadsheet I used in the video and also text files containing the macros used below. https://filedb.experts-exchange.com/incoming/2017/03_w12/1151775/Permutations.txt https://filedb.experts-exchange.com/incoming/201…
###### Suggested Courses
Course of the Month12 days, 23 hours left to enroll