# Need help with my standard deviation code.

• April 16th, 2011, 02:01 PM
drew.field
Need help with my standard deviation code.
Here is the data set that is given as an example:

1 2 3 4.5 5.6 6 7 8 9 10

They give the answer as: 2.99794

Here is my code:
Code Java:

```import java.util.*; public class Exercise05_21 { public static void main(String [] args){ Scanner s = new Scanner(System.in);   System.out.print("Enter ten numbers: ");   double[]x = new double[10];   int i;   for(i = 0;i < 10; i++){   x[i] = s.nextDouble(); }     double mean = mean(x, i);   double deviation = var(x);   System.out.println("The mean is " + mean);   System.out.println("The standard deviation is " + deviation);   }   public static double sum(double[] a) { double sum = 0.0; for (int i = 0; i < a.length; i++) { sum += a[i]; } return sum; }               public static double mean(double[]x, double i){   if (x.length == 0) return Double.NaN; double sum = sum(x); return sum / x.length; }             public static double var(double[] x) { if (x.length == 0) return Double.NaN; double avg = mean(x, 10); double sum = 0.0; for (int i = 0; i < x.length; i++) { sum += (x[i] - avg) * (x[i] - avg); } return sum / (x.length - 1); }     }```

I am not sure if my code is just wrong, if I am using the incorrect formula for standard deviation, or both. I've been working on this all freakin day and my head is about to explode. I suck at this stuff. If anyone can help I'd really appreciate it.
• April 16th, 2011, 02:36 PM
helloworld922
Re: Need help with my standard deviation code.
Quote:

Code Java:

`return sum / (x.length - 1);`

You forgot to take the square root.
• April 16th, 2011, 03:01 PM
drew.field
Re: Need help with my standard deviation code.
That did it! Thanks so much.