Function            stddev - calculate the standard deviation of a
                                 set of reals

  Syntax              double stddev(int n, double element[]);

  Prototype in        mathhk.h

  Remarks             variance calculates the standard deviation of a set
                      of n numbers of type double.

  Return value        returns the standard deviation of a set of n
                      numbers.

  See also            average(), summation(), variance()

  Example             #include <mathhk.h>

                      main()
                      {
                           double num[] = { 2.3, 7.1, 6.05 };

                           printf("Std dev is %.9lf\n",stddev(3,num));
                      }

  Program output      Std dev is 2.060339778