How to Calculate Standard Deviation through a Java program ?.

Program to Calculate Standard Deviation in Java

package com.hubberspot.example;


public class StandardDeviation {

 public static void main(String[] args) {

  double[] numbers = new double[10];

  // Take the 10 numbers in array for which we 
  // want to calculate the standard deviation
  numbers[0] = 23;
  numbers[1] = 92;
  numbers[2] = 46;
  numbers[3] = 55;
  numbers[4] = 63;
  numbers[5] = 94;
  numbers[6] = 77;
  numbers[7] = 38;
  numbers[8] = 84;
  numbers[9] = 26;

  System.out.println("1. Get the mean of numbers. The mean is : ");

  double sum = 0;

  // Taking the average to numbers
  for(int i =0; i< numbers.length; i++) {
   sum = sum + numbers[i];
  }

  double mean = sum/numbers.length;

  System.out.println(mean);

  System.out.println("\n2. Get deviation of mean from each number : ");

  double[] deviations = new double[10];

  // Taking the deviation of mean from each numbers
  for(int i = 0; i < deviations.length; i++) {
   deviations[i] = numbers[i] - mean ; 
   System.out.printf("%2.2f",deviations[i]);
   System.out.print(" ");   
  }

  System.out.println();
  System.out.println("\n3. Get squares of deviations : ");
  double[] squares = new double[10];

  // getting the squares of deviations
  for(int i =0; i< squares.length; i++) {
   squares[i] = deviations[i] * deviations[i];
   System.out.printf("%4.2f",squares[i]);
   System.out.print(" ");
  }

  System.out.println();
  System.out.println("\n4. Get addition of squares : ");

  sum = 0;

  // adding all the squares
  for(int i =0; i< squares.length; i++) {
   sum = sum + squares[i];
  }

  System.out.println(sum);

  // dividing the numbers by one less than total numbers
  System.out.println("\n5. Divide addition of squares by total (numbers) - 1 : ");
  double result = sum / (numbers.length - 1);

  System.out.printf("%4.2f",result);

  double standardDeviation = Math.sqrt(result);
  
  // Taking square root of result gives the
  // standard deviation
  System.out.println("\n\n6. Take the square root of result which gives");
  System.out.println("the Standard Deviation of the ten numbers : ");
  System.out.printf("%4.2f",standardDeviation);

 }

}

Output of the program : 

 




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