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第一步算平均值为什么不用几何平均而用算数平均数
NO.PZ2015121802000021问题如下Calculate the stanrviation of annureturns on investment baseon the following chart:A.1.2%.B.4.44%.C.19.7%.B is correct.Meannureturn = (4% - 3% - 4% + 3% + 6%) / 5 = 1.2%Squareviations from the mean: 4%-1.2%=2.8% (2.8%)2= 7.84-3% -1.2% = -4.2% (-4.2%)2 = 17.64-4% -1.2% = -5.2% (-5.2%)2 = 27.043% -1.2% =1.8% (1.8%)2= 3.246% -1.2% = 4.8% (4.8%) 2= 23.04Sum of squareviations = 7.84 + 17.64 + 27.04 + 3.24+ 23.04 = 78.8Sample varian= 78.8/(5 - 1) = 19.7Sample stanrviation = 19.71/2= 4.44%什么时候要除n-1 什么时候除n
NO.PZ2015121802000021 问题如下 Calculate the stanrviation of annureturns on investment baseon the following chart: A.1.2%. B.4.44%. C.19.7%. B is correct.Meannureturn = (4% - 3% - 4% + 3% + 6%) / 5 = 1.2%Squareviations from the mean: 4%-1.2%=2.8% (2.8%)2= 7.84-3% -1.2% = -4.2% (-4.2%)2 = 17.64-4% -1.2% = -5.2% (-5.2%)2 = 27.043% -1.2% =1.8% (1.8%)2= 3.246% -1.2% = 4.8% (4.8%) 2= 23.04Sum of squareviations = 7.84 + 17.64 + 27.04 + 3.24+ 23.04 = 78.8Sample varian= 78.8/(5 - 1) = 19.7Sample stanrviation = 19.71/2= 4.44% 老师这道题用计算器好像很快?我直接按x1, x2, x3...计算器显示Sx=4.438468?
NO.PZ2015121802000021 问题如下 Calculate the stanrviation of annureturns on investment baseon the following chart: A.1.2%. B.4.44%. C.19.7%. B is correct.Meannureturn = (4% - 3% - 4% + 3% + 6%) / 5 = 1.2%Squareviations from the mean: 4%-1.2%=2.8% (2.8%)2= 7.84-3% -1.2% = -4.2% (-4.2%)2 = 17.64-4% -1.2% = -5.2% (-5.2%)2 = 27.043% -1.2% =1.8% (1.8%)2= 3.246% -1.2% = 4.8% (4.8%) 2= 23.04Sum of squareviations = 7.84 + 17.64 + 27.04 + 3.24+ 23.04 = 78.8Sample varian= 78.8/(5 - 1) = 19.7Sample stanrviation = 19.71/2= 4.44% 第二个问题,为啥sample是除以n-1,数量学科有这个公式但太久了记不清了,谢谢老师
NO.PZ2015121802000021 问题如下 Calculate the stanrviation of annureturns on investment baseon the following chart: A.1.2%. B.4.44%. C.19.7%. B is correct.Meannureturn = (4% - 3% - 4% + 3% + 6%) / 5 = 1.2%Squareviations from the mean: 4%-1.2%=2.8% (2.8%)2= 7.84-3% -1.2% = -4.2% (-4.2%)2 = 17.64-4% -1.2% = -5.2% (-5.2%)2 = 27.043% -1.2% =1.8% (1.8%)2= 3.246% -1.2% = 4.8% (4.8%) 2= 23.04Sum of squareviations = 7.84 + 17.64 + 27.04 + 3.24+ 23.04 = 78.8Sample varian= 78.8/(5 - 1) = 19.7Sample stanrviation = 19.71/2= 4.44% 题目中并没有明确是样本还是总体,如何判断是样本?考试中未明确的是否都按照样本(即n-1)处理?
NO.PZ2015121802000021问题如下Calculate the stanrviation of annureturns on investment baseon the following chart: A.1.2%. B.4.44%. C.19.7%. B is correct.Meannureturn = (4% - 3% - 4% + 3% + 6%) / 5 = 1.2%Squareviations from the mean: 4%-1.2%=2.8% (2.8%)2= 7.84-3% -1.2% = -4.2% (-4.2%)2 = 17.64-4% -1.2% = -5.2% (-5.2%)2 = 27.043% -1.2% =1.8% (1.8%)2= 3.246% -1.2% = 4.8% (4.8%) 2= 23.04Sum of squareviations = 7.84 + 17.64 + 27.04 + 3.24+ 23.04 = 78.8Sample varian= 78.8/(5 - 1) = 19.7Sample stanrviation = 19.71/2= 4.44%老师这道题在组合后面的练习题做到了为什么不能用求TWRR那种几何平均直接相乘开根号减一那样算呢