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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:

Standard Deviation

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

ApplicationApplication: 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:
     
    Standard Deviation
    Control Name Text
    Label Label   Value:
    TextBox ListBox txtValue  
    Button Button btnAdd Add
    ListBox Label lbxValues  
    Button Button btnClear Clear
    Label Label   Standard Deviation:
    TextBox Text Box txtStandard Deviation  
    Button 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++)
                    lbxValues.Items.Add(values[i]);
            }
        }
    }
  11. Return to the form
  12. Double-click the Add button
  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
            values.Add(value);
            // 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");
    }
  14. Return to the form
  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();
    }
  17. Return to the form
  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
     
    Standard Deviation
     
    Standard Deviation
  22. Close the form and return to your programming environment

Application

 

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