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**X1, X2,...,X16 are independent and normally distributed, where mean value is 80 and variance is 18^2. Let Y = X1 + X2 + ... + X16. Calculate**

i) P(X1 > 90)

ii) E(Y)

iii) Var(Y)

iv) P(Y>16*90)

i) P(X1 > 90)

ii) E(Y)

iii) Var(Y)

iv) P(Y>16*90)

i) 0.288, easy

ii) E(Y) = 16*80 = 1280

iii) Var(Y) = Var(16*Var(X)) = 16^2 * 18^2 (WRONG!)

Any suggestions?