See this example: http://www.derivante.com/2009/09/01/php-content-rating-confidence/ http://www.derivante.com/2009/09/01/php-content-rating-confi... However, i

See this example: http://www.derivante.com/2009/09/01/php-content-rating-confidence/ http://www.derivante.com/2009/09/01/php-content-rating-confi... However, if you install the stats package for PHP you can use stats_cdf_normal() as well.