private void button4_Click(object sender, EventArgs e)
        {
            float[] data = new float[] { 290, 517, 850, 484, 856, 784, 666, 865, 445, 243 };//不定长数组
            float 样本标准差, 总体标准差;
            STDEV(data,out 样本标准差,out 总体标准差);
            MessageBox.Show(样本标准差.ToString() + "," + 总体标准差.ToString());
        }


        /// <summary>
        /// 样本标准差和总体标准差计算

        /// </summary>
        /// <param name="arrData">数据数组</param>
        /// <param name="std_dev">样本标准差</param>
        /// <param name="STDP">总体标准差</param>
        public void STDEV(float[] arrData,out float std_dev,out float STDP) //计算标准偏差
        {
            float xSum = 0F;//样本总和
            float xAvg = 0F;//样本平均值
            float sSum = 0F;//方差的分子

            //float tmpStDev = 0F;
            int arrNum = arrData.Length;//得到样本数量，分母
            for (int i = 0; i < arrNum; i++)//循环计算得到样本总和
            {
                xSum += arrData[i];
            }
            xAvg = xSum / arrNum;//计算得到样本平均值
            for (int j = 0; j < arrNum; j++)//得到方差的分子
            {
                sSum += ((arrData[j] - xAvg) * (arrData[j] - xAvg));
            }
            std_dev = Convert.ToSingle(Math.Sqrt((sSum / (arrNum - 1))).ToString());//样本标准差

            STDP = Convert.ToSingle(Math.Sqrt((sSum / arrNum)).ToString());//总体标准差
        }