CODEWITHSUNDEEP
arrayseclipsestandard-deviation
Ryan Horner
Ryan Horner

Reputation: 123

Standard Deviation outputting as 0, how to fix?

My Standard deviation in this program is outputting as 0 and I don't know what I'm doing wrong. I've been stuck on this for hours, please help.

public static void main(String args[])
{
    Scanner scan = new Scanner(System.in);

    System.out.println("How many numbers do you want to calculate?");
    int n = scan.nextInt();

    double a[] = new double[(int) n];       // casting n to a double
    double sum = 0.0;
    double sd = 0.0;

    System.out.println("Fill in the values for all " + n + " numbers.");
    for(int i = 0; i < a.length; i++)
    {
        a[i] = scan.nextDouble();
        sum = sum + a[i];
    }

    double average = sum/a.length;

    for(int i = 0; i < a.length; i++)
    {
           a[i] = Math.pow((a[i]-average),2);       // need help here
    }


    System.out.println("The Mean of the " + n +" numbers is " + average);
    System.out.println("The Standard Deviation of the " + n + " numbers is " + sd);
}

Upvotes: 0

Views: 35

Answers (1)

Nick Dahiya
Nick Dahiya

Reputation: 13

Here is a fiddle

Also I have modified your code which should work now and give you correct result.

public static void main(String args[])
{
    Scanner scan = new Scanner(System.in);

    System.out.println("How many numbers do you want to calculate?");
    int n = scan.nextInt();

    double a[] = new double[(int) n];       // casting n to a double
    double sum = 0.0;
    double sqrSum = 0.0;
    double sd = 0.0;

    System.out.println("Fill in the values for all " + n + " numbers.");
    for(int i = 0; i < a.length; i++)
    {
        a[i] = scan.nextDouble();
        sum = sum + a[i];
    }

    double average = sum/a.length;

    //Perform the Sum of (value-avg)^2
    for(int i = 0 ; i < a.length ; i++)
    {
        sqrSum = sqrSum + Math.pow( a[i] - average, 2);
    }
    sd = Math.sqrt(sqrSum / (a.length - 1));


    System.out.println("The Mean of the " + n +" numbers is " + average);
    System.out.println("The Standard Deviation of the " + n + " numbers is " + sd);
}

Upvotes: 1

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