private double 표준편차1(double[] numbers)
        {
            double mean = numbers.Average();
            double sdev = Math.Sqrt(numbers.Average(n => { double dif = n - mean; return dif * dif; }));

            return sdev;
        }

        private double 표준편차2(double[] numbers)
        {
            int n = numbers.Length; // 입력된 데이터 수

            double mean, variance, stddev; //평균분산표준편차

            double total = 0.0d, totalxsq = 0.0d;  //총합계데이터제곱합

            for (int i = 0; i < n; i++)
            {
                total += numbers[i];

                totalxsq += (double)Math.Pow((double)numbers[i], 2);
            }

            mean = total / n;

            variance = (totalxsq - ((double)Math.Pow((double)total, 2) / n)) / (n - 1);

            stddev = (double)Math.Sqrt((double)variance);

            return stddev;
        }