转自：https://physics.stackexchange.com/questions/366367/how-to-calculate-the-sigma-level-between-two-normal-distribution
问题：
Recently, the improved local measurement 
km s
Mpc
from Riess et al. 2016 (hereafter R16) exhibits a stronger tension with the Planck 2016 release 
km sMpc (hereafter P15) at the 
level. ... The value of the Hubble constant 
is consistent with the P15’s result at the 
confidence level.
How do we figure 
and level out?
解决：
Trivially, if you have 
and 
, then 
can be determined (assuming the usual approximations of independent uncertainties that are normally distributed) with a precision of %5E2%2B(%5Cdelta%20B)%5E2%7D%7D)
.
In this case, the difference in the two determinations of 
is 
km/s per Mpc. i.e. different from zero by 3.4 error bars. The σ refers to the size of the uncertainty ; or more specifically, it represents the 68% confidence interval in a normal distribution.
计算过程：
%7D%7D%7B%5Csqrt%7B0.62%5E2%20%2B%200.92%5E2%7D%7D%20%5Capprox%20%5Cfrac%7B1.41%7D%7B1.11%7D%20%5Capprox%201.27)
