Wilson Score

Simple, dependency-free Wilson score

Inspired by How Not To Sort By Average Rating by Evan Miller

How to Use

3 positive ratings out of 5 with 95% confidence

WilsonScore.lower_bound(3, 5)

Continuity correction can improve the score, especially for a small number of samples (n < 30). As of version 0.1.0, it is enabled by default. To disable continuity correction, use:

WilsonScore.lower_bound(3, 5, correction: false)

The default confidence level is 95%. To change this, use:

WilsonScore.lower_bound(3, 5, confidence: 0.99)

To get the full interval, use:

WilsonScore.interval(3, 5)

Star Ratings

You have a rating system where users can rate products from 1 to 5 stars.

A product has two ratings - one 4 star and one 5 star.

average_rating = 4.5
total_ratings = 2
rating_range = 1..5  # 1 to 5 stars

WilsonScore.rating_lower_bound(average_rating, total_ratings, rating_range)

Installation

Add this line to your application's Gemfile:

gem 'wilson_score'

And then execute:

bundle

Additional Resources

• http://www.vassarstats.net/prop1.html
• http://www.goproblems.com/test/wilson/wilson.php

Contributing

Everyone is encouraged to help improve this project. Here are a few ways you can help:

• Report bugs
• Fix bugs and submit pull requests
• Write, clarify, or fix documentation
• Suggest or add new features