Cham - 1 year ago 107

Java Question

Hi I have created a code to calculate the standard deviation of a set of numbers, here my code below:

`public class standardDev {`

public static void main(String[] args) {

Scanner in = new Scanner(System.in);

int n = in.nextInt();

int[] arr = new int[n];

double sum = 0.0;

for(int i = 0; i < n; i++) {

arr[i] = in.nextInt();

}

Arrays.sort(arr);

double median = n % 2 != 0 ? arr[n/2] : (arr[n/2] + arr[(n/2)-1])/2;

for(int i = 0; i < n; i++) {

sum += Math.pow(arr[i] - median,2);

}

System.out.printf("%.1f", Math.sqrt(sum/n));

}

}

However when the input is this:

10

64630 11735 14216 99233 14470 4978 73429 38120 51135 67060

I get a different result from the expected answer.

My output:

`30475.6`

Expected output:

`30466.9`

But if I tried the input below I get the correct answer:

5

10 40 30 50 20

My output:

`14.1`

Expected output:

`14.1`

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Answer Source

Rewrote your code to actually calculate the standard deviation, which is based on the mean:

```
import java.util.*;
import java.lang.*;
import java.io.*;
class standardDev
{
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
int n = in.nextInt();
int[] arr = new int[n];
double sum = 0.0;
double mean = 0;
for(int i = 0; i < n; i++) {
arr[i] = in.nextInt();
mean += arr[i];
}
mean /= n;
for(int i = 0; i < n; i++) {
sum += Math.pow(arr[i] - mean,2);
}
System.out.printf("%.1f", Math.sqrt(sum/n));
}
}
```

Example: http://ideone.com/qY1wkw

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