Desviacion Estandar Y Varianza C#

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace ConsoleApplication37

{

class Program

{

static void Main(string[] args)

{

string[] ar;

ar = new string[10];

for (int i = 0; i < ar.Length; i++)

{

Console.WriteLine(" número {0}", i + 1);

ar[i] = Console.ReadLine();

if (ar[i] == "")

{ ar[i] = "0"; }

}

Console.WriteLine("desviacion standar = {0}", desviacion(ar));

Console.WriteLine("promedo = {0}", prom(ar));

Console.WriteLine("varianza = {0}", varianza(ar));

Console.ReadLine();

}

static double prom(string[] ar)

{

double suma = 0, prom = 0;

for (int i = 0; i < ar.Length; i++)

{

suma += Convert.ToDouble(ar[i]);

}

prom = suma / ar.Length;

return prom;

}

static double desviacion(string[] ar)

{

double d = 0, sumatoria = 0;

for (int i = 0; i < ar.Length; i++)

{

sumatoria += Math.Pow(((Convert.ToDouble(ar[i])) - prom(ar)), 2);

}

d = Math.Sqrt((sumatoria) / (ar.Length - 1));

return d;

}

static double varianza(string[] ar)

{

double v;

v = Math.Pow(desviacion(ar), 2);

return v;

...