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<?php
declare(strict_types=1);
namespace Phpml\Math\Statistic;
/**
* In probability theory and statistics, variance is the expectation of the squared deviation of a random variable from its mean.
* Informally, it measures how far a set of (random) numbers are spread out from their average value
* https://en.wikipedia.org/wiki/Variance
*/
final class Variance
{
* Population variance
* Use when all possible observations of the system are present.
* If used with a subset of data (sample variance), it will be a biased variance.
*
* ∑⟮xᵢ - μ⟯²
* σ² = ----------
* N
public static function population(array $population): float
return StandardDeviation::sumOfSquares($population) / count($population);
}
php-ai /
php-ml
