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STAT2001/STAT2013/STAT6013/STAT6039 - Introductory Mathematical Statistics
发布时间:2022-10-17
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STAT2001/STAT2013/STAT6013/STAT6039 - Introductory Mathematical Statistics (for Actuarial Studies)/Principles of Mathematical Statistics (for Actuarial Studies)
Assignment 2 Semester 2 (2022)
Problem 1
Luke receives 12 WhatsApp messages in total per week (over a 7 day period). Assume that the WhatsApp message arrival times are uniformly distributed across the given week and each WhatsApp message arrives independently of the other messages. Find the probability that at least one WhatsApp message is received on all 7 days.
Problem 2
(a) Let Y1 ,Y2 ,Y3 ,Y4 ,Y5 be an independent and identically distributed sample of size n = 5 from a normal distribution with mean µ = 0 and variance σ 2 = 1 and let = (1/5) 对i(5)=1 Yi and U =对i(5)=1 (Yi −
)2 . Let Y6 be another independent observation from the same normal distribution. What is the distribution of V = 2U − 1 (5
2 + Y62 )? Why?
(b) Let Y1 ,Y2 ,Y3 ,Y4 ,Y5 be an independent and identically distributed sample of size n = 5 from an exponential distribution with mean µ = 2. Find a number c such that
P ( Yi > c) = 0.05.
Problem 3
Assume that the random variable Y has pdf given by
f(y) = {
(a) Find the pdf for U = Y2 .
(b) Use the result of part (a) to find E(Y) and Var(Y).
(c) Let Y1 ,Y2 , . . . ,Yn be a set of independent random variables each with the same marginal distribution as Y above. Find the maximum likelihood estimator of γ = θ4 .
Problem 4
Let Y1 ,Y2 , . . . ,Yn be an independent and identically distributed sample from a distribution with probability density function
f(y) =
where θ is an unknown, positive constant.
(a) Find an estimator θˆ1 for θ by the method of moments.
(b) Find an estimator θˆ2 for θ by the method of maximum likelihood estimation.
(c) Adjust θˆ1 and θˆ2 so that they are unbiased. Find the efficiency of the adjusted θˆ1 relative to the adjusted θˆ2 .