A better average

    double variance(long long *x, int n)

    {

            double m = x[0];

            double s = 0;

            int i;

            for (i=0; i                    double m_new = m + (x[i] - m)/(i+1);

                    s = s + (x[i] - m)*(x[i] - m_new);

                    m = m_new;

            }

            return s / (n - 1);

    }



    double mean(long long *x, int n)

    {

            double m = x[0];

            int i;

            for (i=0; i                    m = m + (x[i] - m)/(i+1);

            }

            return m;

    }



    double stddev(long long *x, int n)

    {

            return sqrt(variance(x, n));

    }



     long long times[30];

   

     printf("mean: %f stddev: %f\n", mean(times, 20), stddev(times, 20));