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| | | Junior Member
 
Group: Forum Members
Last Login: 4/25/2005 8:39:00 AM
Posts: 12, Visits: 1 |
| i saw this in another forum and i thought that it would be useful to the some of you. and no, this is not from the society's website. haha.
"Hi, guys. There’s another important Steel Cage match. Pillow, who knocked me out last round, can use your help. If you appreciate the help I've tried to give you on course P, please vote for Pillow here.
And here’s another practice problem, so that I can justify doing this campaigning in the Exam areas:
Let random variables P and U be votes cast for Pillow and Urysohn respectively.
P is normal with mean 120, variance 10.
U is normal with mean 100, variance 10.
Cov(P,U) = -5
Phi(x) denotes the cumulative distribution function of the standard normal distribution.
Using the normal approximation, with continuity correction, what is the probability that Pillow wins by at least 12 votes?
[I’m not sure whether continuity correction is on course 1. Since the election result is a discrete distribution, your estimate of the probability Pillow wins by at least 12 is the probability that the normal approximation to her margin of victory is at least 11.5. If you just take the normal distribution result closest to 12, you’ll be close enough here.]
(A) Phi(-2.69)
(B) Phi(-1.70)
(C) Phi(-1.55)
(D) Phi(+1.55)
(E) Phi(+2.69)
Answer D. Which is the same as 1 – Phi(-1.55). P – U is normal with mean 20 and variance 30. Without continuity correction, the answer would be Phi(1.46)."
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yes! i'm still alive |
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