#Rewritten code from /r2/r2/lib/db/_sorts.pyx
from math import sqrt
def _confidence(ups, downs):
n = ups + downs
if n == 0:
return 0
z = 1.0 #1.0 = 85%, 1.6 = 95%
phat = float(ups) / n
return sqrt(phat+z*z/(2*n)-z*((phat*(1-phat)+z*z/(4*n))/n))/(1+z*z/n)
def confidence(ups, downs):
if ups + downs == 0:
return 0
else:
return _confidence(ups, downs)