It seems to work as described in the article: require 'rubygems' require 'statistics2' def ci_lower_bound(pos, n, power) if n == 0

It seems to work as described in the article: require 'rubygems' require 'statistics2' def ci_lower_bound(pos, n, power) if n == 0 return 0 end z = Statistics2.pnormaldist(1-power/2) phat = 1.0*pos/n (phat + z*z/(2*n) - z * Math.sqrt((phat*(1-phat)+z*z/(4*n))/n))/(1+z*z/n) end puts ci_lower_bound(60, 100, 0.10) # => 0.517809505446319 puts ci_lower_bound(500, 1000, 0.10) # => 0.474027691168875 puts ci_lower_bound(50, 100, 0.10) # => 0.418847795168265 The top ranked result has 60 positives out of 100, and beats 500 out of 1000 - almost 10 times as many positive votes.