StatisticalLinq.cs

using System.Linq;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace StatisticalLinq
{
    [TestClass]
    public class VarianceTest
    {
        [TestMethod]
        public void VarianceOf10Numbers()
        {
            var result = Enumerable.Range(1, 10)
                .Select(i => (decimal)i)                // Cast
                .Select(i => new                        // Map
                {
                    N2 = i*i,
                    N1 = i,
                    N0 = 1
                })
                .Aggregate((a1, a2) => new              // Reduce
                {
                    N2 = a1.N2 + a2.N2,
                    N1 = a1.N1 + a2.N1,
                    N0 = a1.N0 + a2.N0
                });
            decimal mean = result.N1 / result.N0;
            decimal variance = (result.N2 - result.N1 * mean) / result.N0;

            Assert.AreEqual(5.5m, mean);
            Assert.AreEqual(8.25m, variance);
        }
    }
}