急 ! F6 M1 統計學1題唔識做 Q6a ?

1. P(x < 5 years) = ? for replacement

Z = (8.2 - 5)/1.1 = 2.91

P(0 < Z < 2.91) = 0.4982

P(Z < -2.91) = 0.5 - 0.4982 = 0.0048







2. warrenty = ? years for 98% not replacement

P(Z < 2.054) = 98%

Z = (8.2 - x)/1.1 = 2.054

x = 8.2 - 2.054*1.1 = 5.9406 years




3. P(4 years < x < 6 years) = ? for not replaecment

Z1 = (8.2 - 4)/1.1 = 3.82

Z2 = (8.2 - 6)/1.1 = 2

P(0 < Z1 < 3.82) ≒ 0.5

P(0 < Z2 < 2) = 0.4772

P(-2 < Z < -3.85) = 0.5 - 0.4772 = 0.0228

P(Z > -2) = 1 - 0.0228 = 0.9772