write a necessary class to calculate variance and standard deviation of n number.

/*
write a necessary class to calculate variance and
standard deviation of n number.
variance=1/n summation(Xi-A.M)2        for all i=1 to n
S.D=sqrt(variance)
where A.M=1/N sumation(Xi)    for i=0 to n
*/
#include<conio.h>
#include<iostream.h>
#include<math.h>
class calc
{
public:calc();
};
calc::calc()
       {
       int mean=0,n,a[10],i,ans=0,sum=0;
       double var,sd,am;
       cout<<"\nenter how many number:-";
       cin>>n;
       cout<<"\nenter the number:-";
       for(i=0;i<n;i++)
       {
       cin>>a[i];
       mean=mean+a[i];
       }
       am=mean/n;
       for(i=0;i<n;i++)
       {
       ans=0;
       ans=(a[i]-am);
       sum=sum+(ans*ans);
       }
       var=(float)sum/n;
       cout<<"\nvariance:-"<<var;
       sd=sqrt(var);
       cout<<"\nstandard deviation:-"<<sd;
       }

int main()
{
clrscr();
calc c;
getch();
return 0;
}
/*

enter how many number:-3

enter the number:-45
67
8

variance:-592.666667
standard deviation:-24.344746
*/