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For reference, at least in particle physics the standard for a discovery is usually taken to be five-sigma, a 1 out of 1.7 million error probability, plus an in
by danbruc 10y ago
For reference, at least in particle physics the standard for a discovery is usually taken to be five-sigma, a 1 out of 1.7 million error probability, plus an independent verification to eliminate systematic errors that would not show up in the statistics.
- ethbro 10y agoFrom someone who hasn't worked with statistics in awhile, isn't sigma partly dependent on the number of independent events? If so, and LIGO detects occur infrequently, how long are we talking about, even assuming the data supports?
- hacker_9 10y agoThe article said two years.
- sleavey 10y agoWe use a technique called time sliding to generate more background data to understand our detector noise better, and thus set better upper limits on the false alarm rate. So even with a 3 month observation time we can claim 5+ sigma.
- ethbro 10y agoThanks for the additional information! I'm assuming you're referring to the method documented in Ch 4 here? https://gwic.ligo.org/thesisprize/2011/capano_thesis.pdf https://gwic.ligo.org/thesisprize/2011/capano_thesis.pdf If so, would it be fair to say (as a simplification) that instead of increasing the confidence in GW events by collecting more of them, you're doing so by holding the number of collected events almost constant and increasing the confidence in the characteristics of noise the detector is reporting?
- sleavey 10y agoYes, exactly that. We don't have the luxury of many events, so to increase our confidence we generate more background. One of the problems is what to do with data that contains more than one event. In the second detection paper, one of the plots contains the background with and without the other event taken into account. This is because during the time sliding process you will necessarily slide the time series from one detector across a gravitational wave signal in the other, producing false background noise. There's no real standard way of dealing with this, so we show both cases - but both claim 5+ sigma.
- kobeya 10y agoThis isn't particle physics. Particle physics has the luxury and burden of dealing with trillions of experimental trials, not a measly 2.