C Program determination of arithmetic mean and standard deviation

Each element of an array is a variable of the type declared for the array. Thus, if an array is declared as int Array [n],all its n elements are of type int, and all the operations that can be done on variables of type int may be carried out on the elements of this array. The same holds for arrays of types float, double, and char. In Program integer array elements are subjected to arithmetic operations.

#include <stdio.h>
#include<math.h>
void main()
{ 
  int x, y, z, i, Sum = 0;
  double Average_value = 0.0 , Sigma= 0.0;
  int Sample[] = {12,13,14,16,13,15,13,17,15,18,15,16,21,13,14};
  clrscr();
  x = sizeof (int);
      y = sizeof (Sample);
     z = y/x;
  for(i=0;i<=(z-1);i++)
     Sum+= Sample[i];
     Average_value = Sum / z;
     Sigma= sqrt(((Sample[i]-Average_value)*(Sample[i]- Average_value)) /(z-1));
     printf("Number of elements= %d\n", z);
     printf("Sum of elements= %d\n", Sum) ;
     printf("Sample average= %f\n", Average_value);
     printf("Sample std. deviation= %f\n", Sigma);
}