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Thread: Problem with a weigted average code

  1. #1
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    Default Problem with a weigted average code

    I am doing a program that has a weighted average calculation and everything compiles and runs. It is just that my weighted average seems to be calculating incorrectly.

    This is the type of output I should see:


    Homework:
    Number of assignments? 3
    Assignment 1 score and max? 14 15
    Assignment 2 score and max? 16 20
    Assignment 3 score and max? 19 25
    Sections attended? 4
    Total points = 65 / 80
    Weighted score = 40.63
    Exam 1:
    Score? 81
    Curve? 0
    Total points = 81 / 100
    Weighted score = 16.2
    Exam 2:
    Score? 95
    Curve? 10
    Total points = 100 / 100
    Weighted score = 30.0
    Course grade = 86.83


    Below is my code and I think even after getting up this morning and looking at it, I have an error in the calculations, but I can;t pinpoint it. Any useful suggestions would be helpful.
    //This program is supposed to receive input from user, and calculated the grades of a
    //student with a weighted average
     
    import java.util.Scanner;
     
    public class Grades{
    	private double weightExam;
    	private double score;
    	private double curveAmount;
    	private double scoreTotal;
    	private double scoreWeighted;
    	private double weightHomeWork; 
    	private int section;
    	private int sections;
    	private double sumScore;
    	private double number;
    	private double assignMax;
    	private double assignScore;
    	private int sumMax;
     
    	Scanner console = new Scanner(System.in);
     
    	public Grades() {
    		intro();
    		exam();
    		homework();
    	}
    	public void intro() {
    		System.out.println("This program accepts scores from two exams and");
    		System.out.println("scores from your homework as input and computes");
    		System.out.println("your grade in the course.");
    		System.out.println();
    	}
    	public void exam() {
    		for (int i = 0; i < 2; i++) { // 2 exams
    			System.out.print("What is the weight of exam " + i + " (0-100)?");
    			weightExam = console.nextInt();
    			System.out.print("Score earned?");
    			score = console.nextInt();
    			System.out.print("Was there a curve (1=yes, 2=no)?");
    			int curve = console.nextInt();
    			if (curve == 1) {
    				System.out.print("How much was the curve?");
    				curveAmount = console.nextInt();
    			} 
    			else {
    				curveAmount = 0;
    			}
    			totalScore();
    			weightedScore();
     
    			System.out.println("Total points = " + scoreTotal + "/" + "100");
    			System.out.println("Weighted score = " + scoreWeighted + "/" + weightExam);
    		}
    	}
    	public void totalScore() {
    		scoreTotal = Math.min(score + curveAmount, 100);
    	}
    	public void weightedScore() {
    		scoreWeighted = (score + curveAmount)/200 * weightExam;
    	}
    	public void homework() {
    		System.out.print("What is the Homework weight (0-100)?");
    		weightHomeWork = console.nextInt();
    		System.out.print("Number of assignments?");
    		number = console.nextInt();
     
    		for (int i = 0; i < number; i++) {
    			System.out.println("Assignment " + i+1 + " score and max?");
    			assignScore = console.nextInt();
    			assignMax = console.nextInt();
    			sumScore += assignScore; 
    			sumMax += assignMax; 
    		}
    		System.out.print("How many sections attended?");
    		section = console.nextInt();
    		sections = Math.min(3 * section, 20);
    		System.out.println("Section points = " + sections);
     
    		weightedHomework();
     
    		System.out.println("Total points = " + (sections + sumScore) + "/"
    				+ sumMax);
    		System.out.println("Weighted score = " + scoreWeighted + "/" + weightHomeWork);
    	}
    	public void weightedHomework() {
    		scoreWeighted = ((sections + sumScore)/sumMax)*weightHomeWork;
    	}
    	public static void main(String[] args) {
    		new Grades();
    	}
    }


  2. #2
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    Default Re: Problem with a weigted average code

    I have an error in the calculations
    Post the program's output or something that shows the error and add some comments saying what the output should be.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Problem with a weigted average code

    We need to understand what you think is wrong or specifically what indications you have that the output is incorrect before we can help.

  4. #4
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    Default Re: Problem with a weigted average code

    I apologize, I had it highlighted to copy and paste, then forgot to add it to the post.

    Output from the program:



    This program accepts scores from two exams and
    scores from your homework as input and computes
    your grade in the course.

    What is the weight of exam 0 (0-100)?20
    Score earned?98
    Was there a curve (1=yes, 2=no)?1
    How much was the curve?5
    Total points = 100.0/100
    Weighted score = 10.3/20.0
    What is the weight of exam 1 (0-100)?30
    Score earned?88
    Was there a curve (1=yes, 2=no)?1
    How much was the curve?10
    Total points = 98.0/100
    Weighted score = 14.7/30.0
    What is the Homework weight (0-100)?50
    Number of assignments?3
    Assignment 01 score and max?
    15 15
    Assignment 11 score and max?
    19 20
    Assignment 21 score and max?
    21 25
    How many sections attended?
    5
    Section points = 15
    Total points = 70.0/60
    Weighted score = 58.333333333333336/50.0

  5. #5
    Super Moderator Norm's Avatar
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    Default Re: Problem with a weigted average code

    What is the error? Can you show what the output should be?
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Problem with a weigted average code

    The mathematical formula should be:
    ((15+19+21+(5x4))/(15+20+25+20))x50 + ((98/100)x20) + ((97/100)x30)

    The first parenthetical x 50 is the sum of the actual grades/the max grades for homework x 50% of the total grade. The second and third parenthetical are each and exam and the x20 and x30 is the percentage of the total grade for those exams.

    I am afraid I know the mathematical but not the coding replacement for those formulas.

  7. #7
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    Default Re: Problem with a weigted average code

    The java expression for that formula is very similiar. The * operator for multiply.

    One problem is integer division: 4/5 = 0 vs float division: 4/5.0 = .8
    Make sure the divisions are not integer by making one of the parts floating
    If you don't understand my answer, don't ignore it, ask a question.

  8. #8
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    Default Re: Problem with a weigted average code

    Thank you! I will go back through it and try to restructure the formulas.

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