/**
 *  This is the cleaned up version of a program to calculate
 *  the average and standard deviation of a list of numbers entered
 *  from the keyboard
 *  
 *  Written by: Stuart Hansen
 *  Date: October 23, 2002
 */

import java.util.*;
    
public class Stats
{
    public static void main (String [] args)
    {
        int count = 0;          // count the number of numbers
        double sum = 0.0;       // Sum the numbers entered
        double sumSqr = 0.0;    // the sum of the squares
        double number;          // The current number
        
        Scanner input = new Scanner(System.in);
    
        // Prime the pump
        System.out.print("Enter a number, negative to terminate: ");
        number = input.nextDouble();
        
        // Continue until the user enters a negative number
        while (number >= 0.0)
        {
            // Add and count
            sum += number;
            sumSqr += number*number;
            count++;
            
            // Enter the next number
            System.out.print("Enter a number, negative to terminate: ");
            number = input.nextDouble();
        }
        
        // Make certain that at least one number was entered before dividing
        if (count > 0)
        {
            // Report the statistics
            double average = sum/count;
            System.out.println("The average is " + average);
            
            double standardDeviation = Math.sqrt(sumSqr/count-average*average);
            System.out.println("The standard deviation is " + standardDeviation);
        }
        else
            System.out.println("No numbers entered!");

    }
}