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肉团诗😋 · 2021年06月26日

题外问题：如何区分问的是sample 的standards deviation 还是population的

  1. CFA I
  2. Portfolio

NO.PZ2015121802000021

问题如下：

Calculate the standard deviation of annual returns on an investment based on the following chart:

选项：

A.

1.2%.

B.

4.44%.

C.

19.7%.

解释：

B is correct.

Mean annual return = (4% - 3% - 4% + 3% + 6%) / 5 = 1.2%

Squared deviations 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 = 27.04

3% -1.2% =1.8%    （1.8%）2= 3.24

6% -1.2% = 4.8%    （4.8%） 2= 23.04

Sum of squared deviations = 7.84 + 17.64 + 27.04 + 3.24+ 23.04 = 78.8

Sample variance = 78.8/(5 - 1) = 19.7

Sample standard deviation = 19.71/2= 4.44%

题外问题：如何区分问的是sample 的standards deviation 还是population的

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2 个答案

丹丹_品职答疑助手 · 2021年09月01日

嗨，爱思考的PZer你好：


同学你好，用sample的数值，题目给了明确的样本情况

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就算太阳没有迎着我们而来，我们正在朝着它而去，加油！

丹丹_品职答疑助手 · 2021年06月27日

嗨，爱思考的PZer你好：


同学你好，一般情况下，如果题目中给出具体的例子，我们会用sample。正常的考题，除了数量科目，其他科目我们可以认为都是population的，本身二者答案结果差的也不多，其他科目不侧重这个

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加油吧，让我们一起遇见更好的自己！

木木RJ · 2021年08月31日

老师，这道题目计算器Sx=4.4%, popluation的结果可是3.96%，所以到底用哪个，有点迷糊

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