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Kyle

Standard Deviation Calculator - Java

Question

So I was bored today and thought to myself 'do you know what I don't enjoy doing? Standard Deviation, so I'm going to make something that does it for me!'. So I did :P Plus it gave me a chance to practice some Java which I seem to be doing a good job of half learning basics, forgetting then coming back to so hopefully I stick at it this time xD Anyway here is the code, do with it what you will - think of it whenever you have to do Standard Deviation, trust me it will save much boredom xD

 

import java.util.Scanner;

class main {

    public static void main(String [] args){

        //Known fields for equation
        double sigX = 0;
        double sigXSq = 0;
        double n;

        //Creates object to scan for user input via keyboard
        Scanner keyBoard = new Scanner(System.in);

        //So that it knows the size needed for the array
        System.out.println("Please enter the number of data there are in the data set:");
        n = keyBoard.nextDouble();
        int number = (int)n;

         //Creates double X array to store data for standard deviation
        double X[];
        X = new double[number];

        //User input of data values
        for(int i=0 ; i < number; i++){
            System.out.println("Please enter number " + (i+1));
            X[i] = keyBoard.nextDouble();
        }
        //to find Sigma X
        for(int i=0; i < number; i++){
            sigX = sigX + X[i];
        }
        //to find Sigma X Squared
        for(int i=0; i < number; i++){
             sigXSq = sigXSq + (Math.pow(X[i], 2));
        }

        //Final Working
        double SDPart1 = sigXSq/n;
        double SDPart2 = Math.pow((sigX/n),2);
        double SD = Math.sqrt((SDPart1-SDPart2));

        //Result
        System.out.println("==========================");
        System.out.println("The standard deviation is:");
        System.out.println(SD);
        System.out.println("==========================");
    }
}

 

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