C E E 5 9 7 – Ri s k A n a l y si s a n d M a n a g e m e n t
Homework Assignment #7
Readings for Highway Safety
National Research Council (NRC), "55: A Decade of Experience,"
Exec. Summary & Appendix material (Packet)
]
Read Lave (one page; packet), "Costs of Going 55" for Wednesday, 3/12/2008
Homework Due Wednesday, March 26, 2008 (after spring break)
1.
Parameter estimation for a Poisson process:
(a) If, on average, airline accidents occur at a rate of 0.152 accidents per million flights
(i.e. 5/33 million flights), what is the probability of exactly 5 accidents between 1979
and 1986, as reported in the table in last week’s homework? [Here passage of time is
measured not in minutes but in flights.] [ 0.15 < p < 0.2 ]
(b) If I started waiting today for another 3 accidents to occur so that I would have more
data for my test, what are the mean and standard dev. of the length of time (in yrs) that
I would have to wait (assuming the accident rate didn't change)? [μ
≈
5 yrs;
σ
≈
3 yrs]
(c) If I estimate the arrival rate
λ
of accidents from 5 accidents in 33 million flights, what
is the estimate of
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 Fall '08
 CARR
 Statistics, Standard Deviation, National Research Council, Risk Analysis and Management, Charles Lave, speed limit change

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