this post was submitted on 15 Sep 2023
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What does 1 sigma mean?
Sigma is basically a representation of certainty that your result isn’t a statistical fluke. It comes from standard deviation in statistics but 1 sigma is 68% certain. 2 sigma is 95%. 3 sigma is 99.7%.
By convention, astronomy uses 3 sigma for “significance,” meaning you almost definitely found something. Particle physics, since it’s usually done in controlled experiments, usually requires 5 sigma (99.99994%).
It’s similar to margin of error in political polls.
All of our homies like 3 sigma.
Oh that's where 6 Sigma comes from. TIL
Why such different gaps in the metric? Nearly 30% difference between sigmas to less than 5% for the next one.
it comes from the shape of the normal distribution (the bell curve) it goes down slowly at first then rapidly and then slowly creeping towards 0 but never getting there.
Thanks
It’s a number that statistically represents how strong the result is in the data basically. As far as I understand it, with astronomy the typical sigma value expected is 3
Technically, this is astrochemistry, not astronomy. I don't know what the expected sigma value there is.
It’s 3 plus/minus 1 sigma
Whats less than 0 sigma? I kid but only a little Astrochemistry is fantastically difficult, it involves large networks of reactions, many of which have multiple orders of magnitudes of uncertainty on their rates. Different groups can tey to model the same conditions and end up with over a factor of 1000 difference in the abundences of key tracer speices.
That's why I'm positive but not excited yet. It's a good sign. We need to see if detecting it can be replicated... although I'm not sure how to do that except with the Webb again.
By saying 1 sigma, they are basically saying tgat are 68% confident in the results. As you increase the sigma, your confidence in the results increases. Here is a site that goes into more in depth explanation: https://news.mit.edu/2012/explained-sigma-0209#