New brain teaser for you

[Ambobeer]

Uuungh? If you test positive then surely its 100%

[JD_975]

I'm intregued as to the correct answer now

[si tate]

1 in 50 then?

[flounderbout]

Uuungh? If you test positive then surely its 100%

It would be if the test was 100% accurate. But it isn't, it's 95% accurate.

[flounderbout]

1 in 50 then?

Give that man a cigar...

[Mork]

OK.
I guess that test is showing that there's a 95% chance that you are the 1 in 1000.

So.
1 in 1000 = 0.1 %
95% X 0.1% = 9.5%

So.
That's a 9.5% chance.

[Predictable Bob]

Explain the maths please Henry !

[si tate]

Give that man a cigar...

Part guess, part working out but when you think about it it's quite simple.

What do I win?

[Mork]

Assume they test all 1000 people.
50 if those people will get a positive result. (95% accurate)
Only one of those 50 will have the disease.

1 in 50 chance of having it.

[flounderbout]

For every 1000 people tested (of whom one will have the disease), there are 50 positive tests (the test is only 95% accurate). So if you test positive, you have a 1/50 chance of being the unlucky one who really has the disease.


Edit - Morked...

[flounderbout]

What do I win?

A soapy backrub from the next closest answer...

[JD_975]

I get it, the test is 95% accurate so out of 1000 people it will say 50 have it yet only one will, simples now lol, so that would be a 2% chance of having the disease

[Mork]

The office where I work has an equal opportunities recruitment policy and several disabled workers.
According to the latest office statistics everyone in my office has on average one testicle and slightly less than 2 legs.

Maths is fun.

[JD_975]

Ahh too late

[si tate]

A soapy backrub from the next closest answer...

I pass on that one "for now"