function PopMeanVariance(int[] calldata x, int[] calldata weights, uint8 precision) returns the the sample mean and biased variance according to the following formulas:
i∑wi∗xi/(sumiwi)
i∑wi(xi−mean)2/(sumiwi)
Lenghts of x and weights have to be equal. Precision represents the number of decimal places and can be set between 0 and 18. It is applied to x, weights and output.