Posts Tagged 'astrophysics'

Confidence in astrophysics

[by JSC5]

This paragraph from an essay by Dennis Overbye on discoveries in astrophysics really blew me away:

“Call it the two-sigma blues. Two-sigma is mathematical jargon for a measurement or discovery of some kind that sticks up high enough above the random noise¬† to be interesting but not high enough to really mean anything conclusive. For the record, the criterion for a genuine discovery is known as five-sigma, suggesting there is less than one chance in roughly 3 million that it is wrong. Two sigma, leaving a 2.5 percent chance of being wrong, is just high enough to jangle the nerves.”

If you think back to your first statistics class, you’ll remember a bunch of ways for testing an observation for significance, and I’ll bet you $10 you used the 95% confidence level for just about everything you did in that class. It’s become the default level for significance in most social sciences. Run the regression, and if p<.05, bam, you’re done. Call it significant and move on.

Then along comes a hard science like astrophysics that puts everyone else to shame. These guys run right past .05¬† without looking back, at .025 their nerves start “jangling”, but it’s not until 3.33 x 10^-7 that they’re ready to go ahead and say, “Excuse me, sir, but I think I have a genuine discovery on my hands.” Meanwhile the economics/poly sci grad student next door has run 1000 new regressions and ‘discovered’ a bunch of things that turn out not to be quite right but still get published with frightening frequency.

And that’s why people trust astrophysicists.

Advertisements

Subscribe by email, feedburner

Subscribe by e-mail

or subscribe with feedburner

This is a group blog. JSC5 currently writes from the US. JSC7 writes from behind the Great Firewall of China.

wordpress statistics

Categories and tags

Archives