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Find Pr[5X - 4Y > 40], given that they are indep&normal, and...?
that mean-x=18, mean-y=14, std dev-x=3, std dev-y =2.
I'm not sure how to go about solving this problem?
sorry, Pr[5X - 4Y >= 40]
2 Answers
- Anonymous10 years agoFavorite Answer
The answer should be...
Pr[5X - 4Y > 40] ≈ 0.36
Good luck!
Source(s): ☻ - GuillermoLv 710 years ago
μx = 18
σx^2 = 9
μy = 14
σy^2 = 4
E(5*X - 4*Y) = 5*E(X) - 4*E(Y) = 5*18 - 4*14 = 34
V(5*x - 4*Y) = 25*V(X) + 16*V(Y) = 25*9 + 16*4 = 289, SD(5*X - 4*Y) = 17
P(((5X - 4Y) - 34)/17 ≥ (40 - 34)/17) = P(Z ≥ 0.35) = P(Z ≤ - 0.35) = 0.3632
Source(s): Standardized Normal Distribution.
