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Dang.D · 2021年10月05日

请问这个题目,对应的书里面的计算公式是什么?

NO.PZ2017092702000073

问题如下:

The probability distribution for a company’s sales is:

The standard deviation of sales is closest to:

选项:

A.

$9.81 million.

B.

$12.20 million.

C.

$32.40 million.

解释:

A is correct.

The analyst must first calculate expected sales as 0.05 × $70 + 0.70 × $40 + 0.25 × $25 = $3.50 million + $28.00 million + $6.25 million = $37.75 million. After calculating expected sales, we can calculate the variance of sales: = σ2 (Sales) = P($70)[$70 – E(Sales)]2 + P($40)[$40 – E(Sales)]2 + P($25)[$25 – E(Sales)]2 = 0.05($70 – 37.75)2 + 0.70($40 – 37.75)2 + 0.25($25 – 37.75)2 = $52.00 million + $3.54 million + $40.64 million = $96.18 million. The standard deviation of sales is thus σ = ($96.18)1/2 = $9.81 million.

请问这个题目,对应的书里面的计算公式是什么?遇到这样的问题老犯错

1 个答案

星星_品职助教 · 2021年10月06日

同学你好,

这道题考察的是计算标准差。根据下方截图里圈出来的公式逐项代入就是答案解析中的这部分:

截图公式如下:


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