Question

Write a test program that prompts the user to enter 10 numbers and displays the mean and deviation, as shown in the following sample run:

Your program should contain the following functions:

// Compute the mean of an array of double values
double mean(const double x[], int size)
// Compute the deviation of double values
double deviation(const double x[], int size)

Write a test program that prompts the user to enter 10 numbers and displays the mean and deviation, as shown in the following sample run:

ex:

Enter ten numbers: 1.9 2.5 3.7 2 1 6 3 4 5 2
The mean is 3.11
The standard deviation is 1.55738

So this what I have:

#include <iostream>
#include <cmath>

using namespace std;

void displayVals(int vals[], int numVals, int sum);
void getVals(int vals[], int numVals);
double average(int sum, int numVals);
double stanDev(int vals[], double mean, int numVals);

int main()
{
   int numVals=10;
   int sum = 0;
   int vals[9];

   getVals(vals, numVals);
   cout << endl;
   displayVals(vals, numVals, sum);
   cout << endl;

}

void getVals(int vals[], int numVals)
{
   int index;
   cout << "Enter ten numbers :" << "\n";
   for (index = 0; index < numVals; index++) {
       cout << index + 1;
       cin >> vals[index];
   }
}

void displayVals(int vals[], int numVals, int sum)
{
   int index;
   for (index = 0; index < numVals; index++) {
       cout << index + 1;
       cout << vals[index] << ".\n";
   }

   cout << endl;
   cout << "The mean is ";
   cout << average(vals, numVals, sum) << ".\n";

   cout << endl;
   cout << "The standard deviation is: ";
   cout << stanDev(vals, numVals, sum) << ".\n";

}

double average(int sum, int numVals)
{
   double dsum = (double)sum;
   double dnumVals = (double)numVals;
   return dsum / dnumVals;
}

double stanDev(int vals[], double mean, int numVals)
{
   double sum = 0, dVals = 0, value = 0, variance = 0;
   for (int i = 0; i < numVals; i++)
   {
       dVals = (double)vals[i];
       value = (dVals - mean)*(dVals - mean);
       sum += value;
       variance = sum / (numVals);
   }
   return sqrt(variance);
}

Answer 1

#include <iostream>
#include <cmath>

using namespace std;

void displayVals(double vals[], int numVals);
void getVals(double vals[], int numVals);
double average(double sum, int numVals);
double stanDev(double vals[], double mean, int numVals);

int main() {
    int numVals = 10;
    double sum = 0;
    double vals[10];

    getVals(vals, numVals);
    cout << endl;
    displayVals(vals, numVals);
    cout << endl;
}

void getVals(double vals[], int numVals) {
    int index;
    cout << "Enter ten numbers : ";
    for (index = 0; index < numVals; index++) {
        cin >> vals[index];
    }
}

void displayVals(double vals[], int numVals) {
    int index;
    double sum = 0;
    for (index = 0; index < numVals; index++) {
        cout << vals[index] << " ";
        sum += vals[index];
    }
    cout << endl;

    cout << "The mean is ";
    cout << average(sum, numVals) << ".\n";

    cout << endl;
    cout << "The standard deviation is: ";
    cout << stanDev(vals, average(sum, numVals), numVals) << ".\n";
}

double average(double sum, int numVals) {
    double dsum = sum;
    double dnumVals = (double) numVals;
    return dsum / dnumVals;
}

double stanDev(double vals[], double mean, int numVals) {
    double sum = 0, dVals = 0, value = 0, variance = 0;
    for (int i = 0; i < numVals; i++) {
        dVals = vals[i];
        value = (dVals - mean) * (dVals - mean);
        sum += value;
    }
    variance = sum / (numVals - 1);
    return sqrt(variance);
}