Quiz HN: Test your biases

https://news.ycombinator.com/item?id=671287

by jibiki • 17 years ago

4 7 17 years ago

news.ycombinator.com

You are the minister of health. Currently, you screen all citizens for cow-flu using test X. You want to add another test, though, and you have two options: test Y or test Z. Test Y is strongly correlated with test X. Test Z is not correlated with test X.

Do you add test Y or test Z?

tokenadult• 17 years ago

Please provide more information. What is the specificity of each test? What is the sensitivity of each test? And how virulent is the disease? And how expensive is each test?

http://en.wikipedia.org/wiki/Sensitivity_and_specificity

http://www.nhhealthcost.org/costByProcedure.aspx

jibiki2• 17 years ago

That's pretty much the right answer.

Let's say all tests cost the same and are 99% specific. Test X is at least 70% sensitive. Test Y and Z have unknown sensitivity.

sharpn• 17 years ago

If there are tests for a binary result (has cow-flu/does not have cow-flu) that are not correlated, one or both of the tests is bad. Further information could confirm or negate the choice of Y or Z (or sticking only with X).

yummyfajitas• 17 years ago

All good tests should be strongly correlated with the presence/absence of swine flue, and hence correlated with each other. So either tests X/Y are broken, or test Z is broken. Or both.

We need to figure out which before answering the question.

jibiki2• 17 years ago

Let's say X and Y are both good tests. Is it still possible you would prefer Z to Y?

cjg• 17 years ago

If Z caught most of the cases that X missed, but not many that X caught then it would be very useful.

philwelch• 17 years ago

My first instinct is to add test Z. Since Y correlates well with X, Z would provide more information.

But if Y is correlated to X, that might indicate something about its sensitivity.

Quiz HN: Test your biases

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