题目
The probability distribution for a company‘s sales is:「huixue_img/importSubject/1564548692676055040.png」The standard deviation of sales is closest to:
选项
A.$9.81 million.
B.$12.20 million.
C.$32.40 million.
答案
A
解析
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:「huixue_img/importSubject/1564548692743163904.png」The standard deviation of sales is thus σ = ($96.18)^1/2 = $9.81 million.
A正确。 分析师必须首先计算预期销售额为0.05×$70＋0.70×$40＋0.25×$25 =$37.75 million。 通过计算期望销售额，可以计算出销售额的方差: σ^2= P(70)(70- E(销售))^2＋P(40)[ 40 - E(销售)]^2＋ P(25)(25- E(销售))^2 = 0.05(70 - 37.75)^2＋0.70(40 - 37.75)^2＋ 0.25(25 - 37.75)^2 = 52 mil＋ 3.54 mil＋40.64 mil = 96.18 mil。 销售的标准偏差是σ=(96.18)^1/2 = 9.81 mil