Microsoft Visual C# Example Application: The Standard Deviation

 Introduction
 Considering a series of values, the standard deviation is the tendency by which the values vary from the mean. To calculate the standard deviation, you can use the following formula:

The factors in this equation are:

 Factor Description x Each of the values used in the series n The number of values in the series x The mean of the values Σ The sum of values s The standard deviation
 Application: Calculating the Standard Deviation
1. Start Microsoft Visual Studio
2. To create a new application, on the main menu, click File -> New Project...
3. In the middle list, click Windows Forms Application
4. Change the Name to StandardDeviation1
5. Click OK
6. In the Solution Explorer, right-click Form1.cs and click Rename
7. Type Exercise.cs and press Enter
8. Design the form as follows:

 Control Name Text Label Value: TextBox txtValue Button btnAdd Add ListBox lbxValues Button btnClear Clear Label Standard Deviation: TextBox txtStandard Deviation Button btnClose Close
9. Double-click an unoccupied area of the form
10. Change the file as follows:
```using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace MeasuresOfCenter
{
public partial class Measures : Form
{
List<double> values;

public Measures()
{
InitializeComponent();
}

private void Measures_Load(object sender, EventArgs e)
{
values = new List<double>();
}

void ShowValues()
{
lbxValues.Items.Clear();

for (int i = 0; i < values.Count; i++)
}
}
}```
13. Implement the event as follows:
```private void btnAdd_Click(object sender, EventArgs e)
{
// This the value that will be added to the text box
double value = 0.00;
double sumForMean = 0.00, bigSum = 0.00, mean = 0.00;
double stdDev = 0.00;

// Check that the user entered a value in the text box
if (txtValue.Text.Length == 0)
{
MessageBox.Show("You must enter a value.", "Standard Deviation");
return;
}

try
{
// Get the value the user entered
value = double.Parse(txtValue.Text);
// Add it to the collection
// Show the values in the list box
ShowValues();

txtValue.Text = "";
txtValue.Focus();
}
catch (FormatException)
{
MessageBox.Show("The value you entered is invalid.",
"Standard Deviation");
}

// Calculate the total for the mean
for (int i = 0; i < values.Count; i++)
sumForMean += values[i];
// Calculate the mean
mean = sumForMean / values.Count;

// Calculate the total for the standard deviation
for (int i = 0; i < values.Count; i++)
bigSum += Math.Pow(values[i] - mean, 2);

// Now we can calculate the standard deviation
stdDev = Math.Sqrt(bigSum / (values.Count - 1));

// Display the values(standard deviationand stuff)
txtCount.Text = values.Count.ToString();
txtSum.Text = sumForMean.ToString("F");
txtMean.Text = mean.ToString("F");
txtStandardDeviation.Text = stdDev.ToString("F");
}```
15. Double-click the Clear button
16. Implement its event as follows:
```private void btnClear_Click(object sender, EventArgs e)
{
values.Clear();
lbxValues.Items.Clear();

txtValue.Text = "";
txtCount.Text = "";
txtSum.Text = "";
txtMean.Text = "";
txtStandardDeviation.Text = "";
txtValue.Focus();
}```
18. Double-click the Close button
19. Implement the event as follows:
```private void btnClose_Click(object sender, EventArgs e)
{
Close();
}```
20. To execute, press F5
21. Enter a few values and click Add after each