Question

我需要创建一个程序来提示用户0-100之间的等级。当他们输入-1时，表示他们已经完成了输入成绩。我需要输入计数，平均值和标准偏差，但是由于某种原因，标准偏差的输出确实不正确。例如，当我两次输入50时，我的标准偏差是494.97。

import java.util.Scanner;
public class Grade {
 public static void main(String[] args) {
  Scanner scanner = new Scanner(System.in);

  System.out.println("Enter a grade between 0-100?");
  int grade = scanner.nextInt();
  int[] grades = new int[100];
  double sum = 0;
  int i = 0;

  while (grade != -1) {
   grades[i] = grade;
   i++;
   sum += grade;
   System.out.println("Enter a grade between 0 100?");
   grade = scanner.nextInt();
  }

  double sumOfDifference = 0;
  double average = sum / i;

  for (int k = 0; k < grades.length; k++) {
   double difference = (grades[k] - average) * (grades[k] - average);
   sumOfDifference += difference;
  }

  double s = Math.sqrt(sumOfDifference / (i - 1));
  System.out.printf("Count: %4d\n", i);
  System.out.printf("Average: %.2f\n", average);
  System.out.printf("Standard Deviation: %.2f\n", s);
 }
}

Answer 1

这里有

for (int k = 0; k < grades.length; k++) {
   double difference = (grades[k] - average) * (grades[k] - average);
   sumOfDifference += difference;
  }

请注意，这会遍历所有等级的元素，包括尚未初始化的元素。可以仅通过检查用户输入的前i个元素来解决此问题。

for (int k = 0; k < i; k++) {
   double difference = (grades[k] - average) * (grades[k] - average);
   sumOfDifference += difference;
  }

使用For循环的标准偏差不会改变

1 个答案: