Program.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace Grubbs
{
    internal class Program
    {
        public static double[] TestData = new double[] { 1.9, 20, 20, 20, 20, 19, 20, 19, 20, 20, 19, 20, 19, 19, 19, 19, 19, 19, 200, 18 };

        private static void Main(string[] args)
        {
            foreach (var ii in Grubbs.GetUnusualData(TestData).ToList())
            {
                Console.WriteLine(ii + 1);
            }
            Console.ReadLine();
        }
    }

    public class Grubbs
    {
        private static double[] GrubbsCon95 = new double[31] { 0, 0, 0, 1.135, 1.463, 1.672, 1.822, 1.938, 2.032, 2.11, 2.176, 2.234, 2.285, 2.331, 2.371, 2.409, 2.443, 2.475, 2.504, 2.532, 2.557, 2.58, 2.603, 2.624, 2.644, 2.663, 2.745, 2.811, 2.866, 2.914, 2.956 };

        private static double[] GrubbsCon99 = new double[31] { 0, 0, 0, 1.155, 1.492, 1.749, 1.944, 2.097, 2.231, 2.323, 2.41, 2.485, 2.55, 2.607, 2.659, 2.705, 2.747, 2.785, 2.821, 2.854, 2.884, 2.912, 2.939, 2.963, 2.987, 3.009, 3.103, 3.178, 3.24, 3.292, 3.336 };
        public static int[] GetUnusualData(double[] WillCamData, int Con = 95)
        {
            List<int> unusualData = new List<int>();

            List<double> WTestData = WillCamData.ToList();

            for (int i = 0; i < WillCamData.Length; i++)
            {
                double[] TestData = WTestData.ToArray();

                double maxd = WTestData.Max();
                double mind = WTestData.Min();

                double standardDeviation = StDev(TestData);
                double mean = WTestData.Average();

                double unusualValue = maxd - mean > mean - mind ? maxd : mind;

                int keyiid = maxd - mean > mean - mind ? WTestData.Count - 1 : 0;
                double gx = Math.Abs((unusualValue - mean) / standardDeviation);

                bool bkeyi = Con == 95 ? gx > Grubbs.GrubbsCon95[TestData.Length] : gx > Grubbs.GrubbsCon99[TestData.Length];
                if (bkeyi)
                {
                    unusualData.Add(WTestData.IndexOf(unusualValue));
                    WTestData.RemoveAt(WTestData.IndexOf(unusualValue));
                }
                else
                {
                    break;
                }
            }
            return unusualData.ToArray();
        }

        public static double StDev(double[] arrData) //计算标准偏差
        {
            double xSum = 0F;
            double xAvg = 0F;
            double sSum = 0F;
            double tmpStDev = 0F;
            int arrNum = arrData.Length;
            for (int i = 0; i < arrNum; i++)
            {
                xSum += arrData[i];
            }
            xAvg = xSum / arrNum;
            for (int j = 0; j < arrNum; j++)
            {
                sSum += ((arrData[j] - xAvg) * (arrData[j] - xAvg));
            }
            tmpStDev = Convert.ToSingle(Math.Sqrt((sSum / (arrNum - 1))).ToString());
            return tmpStDev;
        }
        public static double CalculateStdDev(IEnumerable<double> values)
        {
            double ret = 0;
            if (values.Count() > 0)
            {
                //  计算平均数   
                double avg = values.Average();
                //  计算各数值与平均数的差值的平方，然后求和 
                double sum = values.Sum(d => Math.Pow(d - avg, 2));
                //  除以数量，然后开方
                ret = Math.Sqrt(sum / values.Count());
            }
            return ret;
        }
    }
}