Pandemic

In Mathland, there is a 1 / 20000 1/20000 chance that any given person might have the deadly 'Super Flu'. Thankfully, it is possible test for the presence of the disease. If a person has the flu, a positive result is certain. However, there is a 1 % 1\% chance of the test giving a false positive. Alice takes the test, and receives a positive result. Worried, she takes another test, and receives another positive result. Which is true of the following statements?

Not enough information. It is likely that Alice does not have the flu. It is likely that Alice has the flu. There is a 50 % 50\% chance that Alice has the flu.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

1 solution

Fin Moorhouse
Apr 4, 2016

The chance of recieving two false positives in a row is 1 100 2 = 1 10000 \frac{1}{100}^2=\frac{1}{10000} . We can see that 1 10000 = 2 1 20000 \frac{1}{10000}=2*\frac{1}{20000} , so it is twice as likely that Alice does not have the flu.

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...