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.
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.
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.
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