Following the rules for standard deviation found at http://en.wikipedia.org/wiki/Standard_deviation
LinkedList<Double> list = new LinkedList<Double>();
double sumOfSquares = 0;
double deviation;
double delta;
list.AddLast(2);
list.AddLast(4);
list.AddLast(4);
list.AddLast(4);
list.AddLast(5);
list.AddLast(5);
list.AddLast(7);
list.AddLast(9);
double average = list.Average();
Console.WriteLine("Average: " + average);
foreach (double item in list)
{
delta = Math.Abs(item - average);
sumOfSquares += (delta * delta);
}
Console.WriteLine("Sum of Squares: " + sumOfSquares);
deviation = Math.Sqrt(sumOfSquares / list.Count());
Console.WriteLine("Standard Deviation: " + deviation); //Final result is 2.0