#include <iostream>
#include <cmath>
#include <ctime>
#include <cstdlib>

using namespace std;
   
int main()
{

double EstWIP = 0;     //estimated # of WIP in system
double EstVAR = 0;        //variance  
int Nrep;     //number of replications
 
    for (Nrep = 0; Nrep <= 200; Nrep++)   
    {   
         int y;
         double sum =0;
         int D = 1000000000; 
         int T = 0;
         int X = 0;
  
        
         srand((unsigned int)time(NULL));
         int A = rand()%5+4;
          
       for (T = 0; T<= 60; T)
       {
              if (D > A)  // part arrives before departs
              {
                    sum = sum + (A-T)*X;     //total time(minutes) spend in system
                    T = A;                   //arrival time is new simulation time
                    X = X + 1;              
                    y = rand()%5+4;          //interarrival time
                    A = T + y;              //next arrival time (update A)
                  
                    if (X == 1)             //If only 1 part in the system
                    {
                         y = rand()%3+2; 
                         D = T + y;           //next departure time (update D)
                    }
                   
              }
              else  // part departs before arrives
              {
                    sum = sum + (D-T)*X;
                    T = D;                    //departure time is new simulatino time
                    X = X-1;         
                    if (X > 0)                //If more than 1 part in system
                    {
                          y = rand()%2+4; 
                          D = T + y;           //next departure time (update D)
                          }
                          else                     //no part in system
                          {
                                                   D = 1000000000;          //big number since no parts in the system
                                                   }
        }
       
               
                    EstWIP = EstWIP + sum/T;  
                    EstVAR = EstVAR + pow(EstWIP-sum, 2);
                    cout <<"Estimate WIP is " <<EstWIP<<endl;     //sometimes T is greater than 60 <---need to fix 
                    cout <<"Estimated VAR is " <<EstVAR<<endl;   
                   
    }
    cout <<"================================================================"<<endl;
    cout <<"Avg Estimated WIP is "<<EstWIP/Nrep<<" parts"<<endl;
    cout <<"Avg Time an entity spends in system is "<<T/(EstWIP/Nrep)<<" minutes"<<endl;
    double Mean = T/(EstWIP/Nrep);
    cout <<"Mean is " <<Mean<<endl;
    double Variance;
    double Sigma;
    Variance = EstVAR/Nrep;
    Sigma = sqrt (Variance);
    cout <<"Estimated Variance is "<<Variance<<endl;
    cout <<"Estimated Standard Deviation is "<<Sigma<<endl;
   
   
}
system("pause");
return 0;         
}

C++ 시작한지 얼마 안된 학생입니다.

    Sigma = sqrt (Variance); 에서 저는 단순히 Variance 값에 루트를 씌우려는건데 더 큰 숫자가 나와버립니다ㅠ.

예를들어 Variance 값이 1.64 얼마였으면 sqrt 한 값은 더 작아야하는데 4059. 얼마가 나와버립니다. 제가 뭘 놓치고 있는걸까요?