Answer 1

Answer 2

这是一个替代实现，有时表现更好，数字化：

        mean = Average(data);
        double sum2 = 0.0, sumc = 0.0;


        for (int i = 0; i < data.Count; i++)
        {
           double dev = data[i] - mean;
           sum2 += dev * dev;
           sumc += dev;
        }

        return (sum2 - sumc * sumc / data.Count) / data.Count;