Question

Java programming:

Write a program called Distribution that reads a file of double values into an array and computes and prints the percentage of those numbers within 1 standard deviation (SD), within 2 SDs, and within 3 SDs of the mean.

The program should be modular and should at least contain the main method and a method for computing the above percentages given the numbers, the mean, and the standard deviation. Other required statistics should be computed in their own methods.

Answer 1

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Distribution {

    public static void main(String args[]){
        Scanner scan;
        //arraylist of type double
        List<Double> input = new ArrayList<Double>();


        try{
            // Please enter the path of the file name you are trying
            // to read double values.
            File file = new File("yourfilename/data.txt");
            scan = new Scanner(System.in);

            // Reading the double values from input file and storing in arraylist of type double
            while(scan.hasNextDouble()){
                double d = scan.nextDouble();
                input.add(d);
            }

            // Percentage of numbers within 1st SD
            double standarddeviation1 = calculateStandardDeviation(input);
            System.out.println("Standard deviation of numbers is " + standarddeviation1);


            double percentagewithSD1 = (calculatenumberswithinSD(input,standarddeviation1) / input.size()) * 100;

            System.out.println("Percentage of numbers below Standard deviation 1 is " + percentagewithSD1);

            // Percentage of numbers within 2nd SD  ==> 2 times SD
            double standarddeviation2 = 2 * calculateStandardDeviation(input);
            System.out.println("Standard deviation of numbers in 2 SDis " + standarddeviation2);

            double percentagewithSD2 = (calculatenumberswithinSD(input,standarddeviation2)  / input.size()) * 100;

            System.out.println("Percentage of numbers below within 2 Standard Deviation is " + percentagewithSD2);

            // Percentage of numbers within 3rd SD  ==> 3 times SD
            double standarddeviation3 = 3 * calculateStandardDeviation(input);

            System.out.println("Standard deviation of numbers within 3 SDs of mean" + standarddeviation3);


            double percentagewithSD3 = (calculatenumberswithinSD(input,standarddeviation3)  / input.size()) * 100;

            System.out.println("Percentage of numbers below within 3 Standard Deviation of mean is " + percentagewithSD3);


        } catch (Exception e1) {
            e1.printStackTrace();
        }

    }

    public static double calculateStandardDeviation(List<Double> dot){
        double total = 0.0, standardDeviation = 0.0;
        int length = dot.size();

        for(double num : dot) {
            total += num;
        }

        //Calculating the average
        double mean = total/length;

        for(double num: dot) {
            standardDeviation += Math.pow(num - mean, 2);
        }

        //returning the standard deviation

        return Math.sqrt(standardDeviation/length);
    }

    //Generic method to calculate the number of array elements below the standard deviation

    public static int calculatenumberswithinSD(List<Double> input,double standarddeviation){
        int totalnumbersbelowstandarddeviation=0;
        for(double num1: input) {
            if(num1 < standarddeviation){
                totalnumbersbelowstandarddeviation++;
            }
        }
        return totalnumbersbelowstandarddeviation;
    }
}