Chapter 5, Problem 1P

Write a function that computes the average and standard deviation of four scores. The standard deviation is defined to be the square root of the average of the four values: (S_i –a)², where a is average of the four scores S₁, S₂, S₃, and S₄. The function will have six parameters and will call two other functions. Embed the function in a driver program that allows you to test the function again and again until you teil the program you are finished.

Program Plan Intro

Creation of program to compute average and standard deviation

Program Plan:

• Define the method “clc()” to calculate value of standard deviation.
  • The variables are been declared initially.
  • The difference of value with average is been computed.
  • The square of resultant value is been computed.
  • The final value is been returned.
• Define the method “stdMean()” to compute value of standard deviation as well as mean of values.
  • The variables are been declared initially.
  • The value of average is been calculated by summing values and dividing it by count of elements.
  • Compute deviations for each value by calling “clc()” method.
  • Compute overall value of deviation and return square root of resultant value.
• Define main method.
  • Declare variables values of scores.
  • Get each value from user.
  • Store values in different variables.
  • Call “stdMean()”to compute standard deviation as well as mean of values.
  • Display standard deviation and mean of values.

Program Description Answer

Program Description:

The following C++ program describes about creation of program to compute mean as well as standard deviation of values entered by user.

Explanation of Solution

Program:

//Include libraries

#include <iostream>

#include <math.h>

//Define function prototypes

double stdMean(double,double,double,double,int, double&);

double clc(double, double);

//Use namespace

using namespace std;

//Define main method

int main()

{

//Declare variables

double s1,s2,s3,s4,avg,sd;

//Get value from user

cout<<"Enter 1st value ";

//Store value

cin>>s1;

//Get value from user

cout<<"Enter 2nd value ";

//Store value

cin>>s2;

//Get value from user

cout<<"Enter 3rd value ";

//Store value

cin>>s3;

//Get value from user

cout<<"Enter 4th value ";

//Store value

cin>>s4;

//Call method

sd=stdMean(s1,s2,s3,s4,4,avg);

//Display message

cout<<"The average is "<<avg<<"\n";

//Display message

cout<<"The standard deviation is "<<sd<<"\n";

//Pause console window

system("pause");

//Return

return 0;

}

//Define method clc()

double clc(double x,double avg)

{

//Declare variable

double tmp;

//Compute value

tmp=x-avg;

//Return value

return tmp*tmp;

}

//Define method stdMean()

double stdMean(double lX1, double lX2,double lX3, double lX4,

int n, double &avg)

{

//Declare variables

double d1,d2,d3,d4,dev;

//Compute value

avg=(lX1+lX2+lX3+lX4)/n;

//Call method

d1=clc(lX1,avg);

//Call method

d2=clc(lX2,avg);

//Call method

d3=clc(lX3,avg);

//Call method

d4=clc(lX4,avg);

//Compute value

dev=(d1+d2+d3+d4)/n;

//Return value

return sqrt(dev);

}

Sample Output

Enter 1st value 8

Enter 2nd value 3

Enter 3rd value 5

Enter 4th value 4

The average is 5

The standard deviation is 1.87083

Press any key to continue . . .