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Drink H · 2020年01月15日

问一道题:NO.PZ2020010302000009

问题如下:

Consider the following data on a discrete random variable X:

a. Calculate the mean and variance of X.

b. Standardize X and check that the mean and variance of X are 0 and 1 respectively.

c. Calculate the skew and kurtosis of X.

选项:

解释:

a. The mean is -0.803 and the variance is 6.762.

b.


c.


Hence, the skew of X is -0.581 and the kurtosis of X is 2.773.

第二部分的后半句,检查均值和方差分别为0,1,这一步如何做?我试着把标准化后的15个值求方差求出来是0.86.

1 个答案
已采纳答案

品职答疑小助手雍 · 2020年01月15日

这其实就是默认是标准化的一部分,标准正态分布的均值为0,标准差为1,那么把参数标准化的过程,也就是把这15个数值计算一下他们分别离均值有多少个标准差。

那1号举例,(-2.456-mean)/标准差=(-2.456+0.803)/2.6= -0.636

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