# calculate the mean and standard deviation of a set of n real numbers using java

import java.util.*;

public class DataSetTester
{
public static void main(String[] args)
{
DataSet a = new DataSet();
Scanner input=new Scanner(System.in);
System.out.println("enter the total number of items");
int m =input.nextInt();
for(int i =1; i <=m; i++)
{
System.out.println("enter the "+i+"  number");
a.add(input.nextInt());
}

System.out.println("count: " + a.getCount());

System.out.println("Mean: " + a.getMean());

System.out.println("standard deviation: " + a.getStandardDeviation());

}

/////////////////////////////

import java.util.ArrayList;
import java.util.List;

public class DataSet {

private List<Double> inputList = new ArrayList();
double x = 0;

public DataSet() {
}

public void add(double x) {

inputList.add(x);

}

public double getMean() {

double sum = getSum();
double count = getCount();
double mean = sum / count;

return mean;

}

public double getSum() {
double sum = 0;

for (double d : inputList) {
sum += d;
}
return sum;
}

public double getStandardDeviation() {

double sum = getSum();

double mean = getMean();
double calc1 = 0;
double calc2 = 0;
double count = getCount();
double stdDeviation = 0;

System.out.println("Sum = " + sum);

for (int i = 0; i < count; i++) {
calc1 = inputList.get(i) - mean;
calc1 = Math.pow(calc1, 2);
calc2 = calc2 + calc1;
}

calc2 = calc2 / (count-1);
stdDeviation = Math.sqrt(calc2);
return stdDeviation;
}

public int getCount() {
return inputList.size();

}
}

output:

enter the total number of items
4
enter the 1  number
1
enter the 2  number
2
enter the 3  number
3
enter the 4  number
4
count: 4
Mean: 2.5
Sum = 10.0
standard deviation: 1.2909944487358056

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