✔ 最佳答案
利用常態分配表
http://www.cust.edu.tw/mathmet/stat/z-dist.pdf
μ = 75, σ = 5
(1)
P(60 < x < 80)
= P([60-75]/5 < z < [80-75]/5)
= P(-3 < z < 1)
= P(-3 < z < 0) + P(0 < z < 1)
= P(0 < z < 3) + P(0 < z < 1)
= 0.4987 + 0.3413
= 0.8400
(2)
P(x < 60)
= P(z < [60-75]/5)
= P(z < -3)
= P(z > 3)
= P(z > 0) - P(0 < z < 3)
= 0.5 - 0.4987
= 0.0013
(3)
P(x < 90)
= P(z < [90-75]/5)
= P(z < 3)
= P(z < 0) + P(0 < z < 3)
= 0.5 + 0.4987
= 0.9987
(4)
P(70 < x < 88)
= P([70-75]/5 < z < [88-75]/5)
= P(-1 < z < 2.6)
= P(-1 < z < 0) + P(0 < z < 2.6)
= P(0 < z < 1) + P(0 < z < 2.6)
= 0.3413 + 0.4953
= 0.8366
2012-12-05 15:57:29 補充:
不同的常態分配表顯示不同的取值範圍,取值方法不同,原理還是相同的。