public static function ratingAverage($positive, $total, $power = '0.05')
{
if ($total == 0)
return 0;
$z = Rating::pnormaldist(1-$power/2,0,1);
//print $z;
$p = 1.0 * $positive / $total;
$to_sqrt = ($p*(1-$p)+$z*$z/(4*$total))/$total;
if ($to_sqrt < 0) {
$to_sqrt = 0.;
}
$sqrt = sqrt($to_sqrt);
$s = ($p + $z*$z/(2*$total) - $z * $sqrt)/(1+$z*$z/$total);
//print "z = $z total = $total p = $p to_sqrt = $to_sqrt s = $s";
//print '($p*(1-$p)+$z*$z/(4*$total))/$total): ' . ($p*(1-$p)+$z*$z/(4*$total))/$total . "\n";
return $s;
}
