Codebits talk proposals rank

gistfile1.rb

require 'rubygems'
require 'json'
require 'net/http'
require 'statistics2'

# from http://www.evanmiller.org/how-not-to-sort-by-average-rating.html
def ci_lower_bound(pos, n, power)
  return 0 if n == 0
  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

url = "http://services.sapo.pt/Codebits/calltalks"
response = Net::HTTP.get_response(URI.parse(url))
results = JSON.parse(response.body)

results.each do |result|
  result["score"] = ci_lower_bound(result["up"].to_i, result["up"].to_i+result["down"].to_i, 0.05)

result["up"].to_f/result["down"].to_f
end

results.sort! { |a,b| b["score"] <=> a["score"] }

results.each_with_index do |result, index|
  puts "##{index+1}"
  puts "Title: #{result["title"]}"
  puts "Votes: #{result["up"]} - #{result["down"]}"
  puts "Score: #{result["score"]}"
  puts
end

I'd be glad if someone pointed me to a decent performance index for this kind of data (upvote/downvote)... ratio doesn't make much sense :)

@SHAD3R that doesn't seem appropriate in this case... talks with more votes are more likely to be accurate than talks with less votes. At the same time, if:
Talk 1: +100 -70
Talk 2: +25 -0
then Talk 1 would be better ranked than Talk 2, and it doesn't seem right IMHO.

@goncalossilva you can give weights to the upvotes according to the downvotes.

If 0 < n downvotes < 25 then n upvotes * 1 end

if 25 < n downvotes < 50 then n upvotes * 0.9 end

Then it's a question of fine tuning this weights

Yeah, I think I'll do something like that... I was waiting for someone to provide me with an already reliable ranking system :)

Apparently what you want is the lower bound of Wilson score confidence interval for a Bernoulli parameter :D

There you go my friend http://www.evanmiller.org/how-not-to-sort-by-average-rating.html

Now that's what I'm talking about! I've seen that before... I think it had something to do with @paulozoom's MSc thesis. Oh well, time for some coding. Thanks!