题目
Using the following Information to answer the question below.「huixue_img/importSubject/1564169387102048256.png」The expected value of Y is closest to:
选项
A.2.1
B.2.2
C.2.3
D.2.4
答案
B
解析
p(Y = 1) = 0.05 + 0.05 + 0.15 = 0.25 p(Y = 2) = 0.05 + 0.10 + 0.15 = 0.30 p(Y = 3) = 0.10 + 0.15 + 0.20 = 0.45 so E(Y) = 1 × 0.25 + 2 × 0.30 + 3 × 0.45 = 2.20 p(Y = 1) = 0.05 0.05 0.15 = 0.25 p(Y = 2) = 0.05 0.10 0.15 = 0.30 p(Y = 3) = 0.10 0.15 0.20 = 0.45 所以 E(Y) = 1 × 0.25 2 × 0.30 3 × 0.45 = 2.20