Question

The following class StatCalc defines a series of methods for computing statistics for a group of numbers.

 /*
 * An object of class StatCalc can be used to compute several simple statistics
 * for a set of numbers.  Numbers are entered into the dataset using
 * the enter(double) method.  Methods are provided to return the following
 * statistics for the set of numbers that have been entered: The number
 * of items, the sum of the items, the average, and the standard deviation
 */
 
public class StatCalc {
 
   private int count;   // Number of numbers that have been entered.
   private double sum;  // The sum of all the items that have been entered.
   private double squareSum;  // The sum of the squares of all the items.
 
   /**
    * Add a number to the dataset.  The statistics will be computed for all
    * the numbers that have been added to the dataset using this method.
    */
   public void enter(double num) {
          count++;
          sum += num;
          squareSum += num*num;
   }
 
   /**
    * Return the number of items that have been entered into the dataset.
    */
   public int getCount() {
          return count;
   }
 
   /**
    * Return the sum of all the numbers that have been entered.
    */
   public double getSum() {
          return sum;
   }
 
   /**
    * Return the average of all the items that have been entered.
    * The return value is Double.NaN if no numbers have been entered.
   */
   public double getMean() {
          return sum / count;
   }
 
   /**
    * Return the standard deviation of all the items that have been entered.
    * The return value is Double.NaN if no numbers have been entered.
    */
   public double getStandardDeviation() {
          double mean = getMean();
          return Math.sqrt( squareSum/count - mean*mean );
   }         
}  // end class StatCalc

Using the StatCalc class, write a program that calculates and then displays as output to the console, the following statistics against the set of numbers given below.

Statistics that must be calculated:

• Count – Quantity of numbers in the data set.
• Mean – The mean or average of the numbers in the data set.
• Standard Deviation – The measure of variance (or dispersion) from the mean.

The set of numbers that you must use is as follows:

5 7 12 23 3 2 8 14 10 5 9 13

You must create a program with a main method that defines the StatCalc class and instantiates an instance of StatCalc called myStatCalc. Your program should instantiate the instance of the StatCalc using a statement similar to the following:

StatCalc myStatCalc;
myStatCalc = new StatCalc();

Answer 1

The Program has been posted here:

/*
* An object of class StatCalc can be used to compute several simple statistics
* for a set of numbers. Numbers are entered into the dataset using
* the enter(double) method. Methods are provided to return the following
* statistics for the set of numbers that have been entered: The number
* of items, the sum of the items, the average, and the standard deviation
*/

public class StatCalc {

private int count; // Number of numbers that have been entered.
private double sum; // The sum of all the items that have been entered.
private double squareSum; // The sum of the squares of all the items.

/**
* Add a number to the dataset. The statistics will be computed for all
* the numbers that have been added to the dataset using this method.
*/
public void enter(double num) {
count++;
sum += num;
squareSum += num*num;
}

/**
* Return the number of items that have been entered into the dataset.
*/
public int getCount() {
return count;
}

/**
* Return the sum of all the numbers that have been entered.
*/
public double getSum() {
return sum;
}

/**
* Return the average of all the items that have been entered.
* The return value is Double.NaN if no numbers have been entered.
*/
public double getMean() {
return sum / count;
}

/**
* Return the standard deviation of all the items that have been entered.
* The return value is Double.NaN if no numbers have been entered.
*/
public double getStandardDeviation() {
double mean = getMean();
return Math.sqrt( squareSum/count - mean*mean );
}   

// Main Method
public static void main(String[] args) {

        //Instance of the Class StatCalc
       StatCalc mystatCalc;
       mystatCalc = new StatCalc();
      
       //Array list as given in the question
       int[] array = new int[] {5, 7, 12, 23, 3, 2, 8, 14, 10, 5, 9, 13};
       int n = array.length;
      
       //Calling enter method to calculate count, sum, mean and Standard Deviation
       for(int i=0;i<n;i++){
           mystatCalc.enter(array[i]);
       }
       //Count – Quantity of numbers in the data set.
       System.out.println("Count = " + mystatCalc.getCount());
      
       //Mean – The mean or average of the numbers in the data set.
       System.out.println("Mean = " + mystatCalc.getMean());
      
       //Standard Deviation – The measure of variance (or dispersion) from the mean.
       System.out.println("Standard Deviation = "+mystatCalc.getStandardDeviation());
      

   }
}

Output screenshot:

  

Code Screenshot:

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