# Thread: attack of the bucolic plague

1. ## attack of the bucolic plague

A dreaded new disease is sweeping the nation. Its called the Bucolic Plague.

A test has been developed that can detect whether you have the disease- the test is 99% ACCURATE. That is if you don't have the disease, that is there will be a 99% chance the test will detect it. If you don't have the disease, the test will be 99% accurate saying you don't.

In the general population, 0.1 percent of people have the disease- thats one-tenth of a percent.

You decide to get the test. you get you resultositive. Now what?

What is the probability you have the disease?

Needs a Tree diagram to lay it out.
what is the sample space?
probabilities for assigned calculations.
probability distribution function
written summary.
word processing report.

2. ## Re: attack of the bucolic plague

I assume you want P(Disease|Positive)=P(D|P)=P(DP)/P(P)

NOW P(DP)=P(P|D)P(D)

and P(D)=P(PD)+P(PD')=P(P|D)P(D)+P(P|D')P(D')

3. ## Re: attack of the bucolic plague

Originally Posted by huskerpowerx3
Needs a Tree diagram to lay it out.
what is the sample space?
probabilities for assigned calculations.
probability distribution function
written summary.
word processing report.
What is the above? Instructions for your report? Is this assessed work?

CB

4. ## Re: attack of the bucolic plague

i think the accuracy of the test is quite low compared to the incidence in the general population, and therefore useless for screening, based on the high (almost 91%) number of false positives.

5. ## Re: attack of the bucolic plague

We can't answer the question since we are told nothing about the accuracy of the test when the subject has the disease. The probability of the subject having the disease given a postiive test result depends also on the probability of a false positive.