standard deviation

[unyime inok]

Please help me figure out why my calStandardDev() is giving an incorrect answer.

import java.io.*;
public class TestRead
{
  
   ReadInteger in = new ReadInteger();    
   final  int numLength = 100;
    int  num [] ;     
    int x = 0;
    double average = 0.0; 
    double sum = 0.0;  
    public TestRead()
    {
     num  = new int[numLength];
     
    }
  

 public double getAvg()
    {
      return average;
    }
    
   //read()- read integers from the file and calculates the average
    public void read()throws IOException{
    while(!in.getEOF())
     if (x < num.length){
         x = x+1;  
         num[x] = in.readInteger(); 
         System.out.println(num[x]);
          //Calculates the average of the numbers in the  file       
          sum += num[x];
          average = sum/(x-1); //end of average calculation      
            
        
      } 
     
    }  
  

 
 //Calculates the standard deviation of the numbers in the file
    public double calStandardDev(int [] num, double average)
    { 
      double standardDev = 0.0;
      if(num.length>0){        
      for(x = 0; x < num.length; ++x){           
        double sd = num[x] - average;
        standardDev += sd*sd;        
      }
         standardDev = Math.sqrt(standardDev/(num.length));//end of sDev 
        
     }
      return standardDev;
    }
    

 
 public void printVal()
    {   
      
       System.out.println("The Average is:" + " " + average);
      
       System.out.println("The Standard is:" + " " + calStandardDev(num,average));
    }
    
    
  
   //main method
   public static void main(String []args)throws IOException{            
               
      
      TestRead  tr = new TestRead();
        tr.read();
        tr.printVal();                 
          
     
  }
}//end of TestRead class
 

[unyime inok]

Please help me figure out why my calStandardDev() is giving an incorrect answer

[Joyce Lee]

Hi Unyime,

Please refer to this similar thread posted by you.

Joyce