样本方差的计算

 1 public class Fangcha {
 2 
 3     public static void main(String[] args) {
 4         double avr = 0;
 5         double sum1 = 0;
 6         double sum2 = 0;
 7         double sum3 = 0;
 8         double[] a = new double[]{0.19 , 0.18 , 0.21 , 0.66 , 0.42 , 0.08 , 0.12 , 0.30 , 0.27 , 0.30};//输入数组
 9 
10         for(int i = 0 ; i<=(a.length-1) ; i++)
11         {
12             sum1 = a[i];
13             sum2 = sum1 + sum2;
14         }
15         avr = sum2/(a.length);
16         System.out.println(avr);
17 
18         sum1 = 0;
19         sum2 = 0;
20         for(int i = 0 ; i <= (a.length-1) ; i++)
21         {
22             sum1 = avr - a[i];
23             sum2 = Math.pow(sum1, 2);
24             sum3 = sum2 + sum3;
25         }
26         avr =sum3/(a.length-1); 
27         System.out.println(avr);
28         
29 
30     }