I have a program and put it below. But the weighted average is not working. The

Question

I have a program and put it below. But the weighted average is not working. The formula is 0.3*grade1 + 0.2 *grade2 + 0.2 * grade3 + 0.3 * grade4, but it is not coming correctly. Also the mean and standard deviation is not working properly can anyone help me out?

#include<iostream>

#include<iomanip>

using namespace std;

void computeGrade(int array[][5]);

void computeMean(double score[], int n, double &mean, double &stdeviation);

int main()

{

     int grades[10][5]={{1,100,100,100,100},{2,100,100,100,90},{3,100,100,90,90},{4,100,90,90,90},{5,90,90,90,90},{6,90,90,90,80},{7,90,90,80,80},{8,90,80,80,80},{9,80,80,80,80},{10,100,90,80,90}};

     computeGrade(grades);

     system("pause");

     return 0;

}

void computeGrade(int array[][5])

{

     double gradetotal=0;

     double gradesum=0.0;

     double eachAvg[10];

     double eachWeightAvg[10];

     double gradetotalavg=0.0;

     double mean1, mean2,sd1, sd2;

     int n=10;

     double score[10];

     cout<<setw(5) <<"StudentID" << setw(10) << "Grade1" << setw(10) << "Grade2" << setw(10) << "Grade3" << setw(10) << "Grade4" <<

           setw(10) <<"Average1" << setw(10) << "Average2" << endl;

     cout<<setprecision(2)<<fixed;

     for(int i=0;i<10;i++)

     {

           gradetotal=0;

           gradesum=0;

           for(int j=0;j<5;j++)

           {

                cout << setw(10)<< array[i][j] ;

                if (j != 0)

                {

                     gradetotal = gradetotal + array[i][j];

                     if ((j == 1) || (j == 4))

                           gradesum = gradesum + (0.3 * array[i][j]);

                     else

                           gradesum = gradesum + (0.2 * array[i][j]);

                }

           }

           eachAvg[i]=gradetotal/4;

           eachWeightAvg[i]=gradesum/4;

           cout<<setw(10)<<eachAvg[i]<<setw(10)<<eachWeightAvg[i];        

           cout<<endl;

     }

     computeMean(eachAvg,10,mean1,sd1);

     computeMean(eachWeightAvg,10, mean2, sd2);

}

void computeMean(double score[], int n, double &mean, double &stdeviation)

{

    double m=0;

    for(int i=0; i<n; i++)

    {

        m+=score[i];

    }

    mean=m/(n*1.0);

     cout << "Mean=" << mean << endl;

     m=0;

    for(int i=0; i<n; i++)

    {

        m+=pow((score[i]-mean), 2);

    }

    double average=m/n;

    double stdeviation=pow(average, 0.5);

     cout<< "Standard Deviation=" << stdeviation << endl;

}

Explanation / Answer

Refer this piece of code :-

#include<stdio.h>
#include<conio.h>
#include<math.h>

void main()
{
    float n,i,mean,var,sd,a[100],temp=0,sum=0;
    clrscr();
    printf("Enter the number of terms:: ");
    scanf("%f",&n);
    printf("Enter the numbers:: ");
    for(i=0;i<n;i++)
    {
        scanf("%f",&a[i]);
    }

    /*..............Mean.............*/
    for(i=0;i<n;i++)
    {
        sum=sum+a[i];
    }
    mean=sum/n;
    printf("Mean=%f ",mean);

    /*.............Variance..........*/
    for(i=0;i<n;i++)
    {
        temp=temp+(a[i]-mean)*(a[i]-mean);
    }
    var=temp/n;
    printf("Variance=%f ",var);

    /*............Standard Deviation........*/
    sd=sqrt(var);
    printf("Standard Deviation=%f ",sd);
    getch();
}

output:

This will give you a better understanding to calculate average and standard deviation

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