Statistical Modelling and Computing
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MATH3821 Statistical Modelling and Computing
Total number of questions 2
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Student Name꞉
Student ID꞉
Question 1 [Total꞉ 9 marks, 3 parts]
Let be a random variable with values in (or or ), and suppose its probability distribution
depends on a single parameter . Then it belongs to the exponential family if it admits the form
for some (measurable) functions and .
Another way of writing this is
where and .
Identify if the following probability density functions belong to the exponential family. If yes, is the
distribution of canonical and what is the natural parameter of this distribution.
a). [3 marks] For the Pareto distribution . Which of the following statement(s) are true.
In [ ]:
In [ ]:
In [ ]:
In [ ]:
Y R N
0
Z f(y; θ)
θ
f(y; θ) = s(y)t(θ)e
a(y)b(θ)
a, b, s, t
f(y; θ) = exp[a(y)b(θ) + c(θ) + d(y)]
s(y) = e
d(y)
t(θ) = e
c(θ)
Y
f(y; θ) = θy
−θ−1
(a) Does not belong to the exponential family of distributions;
(b) Belongs to the exponential family of distributions and is of cannonical form with natural parameter꞉
;
(c) Belongs to the exponential family of distributions but is not of cannonical form;
(d) Belongs to the exponential family of distributions and is of cannonical form with natural parameter꞉
.
Answer꞉
b). [3 marks] For the Exponential distribution꞉ . Which of the following statement(s) are
true.
(a) Does not belong to the exponential family of distributions;
(b) Belongs to the exponential family of distributions and is of cannonical form with natural parameter꞉
;
(c) Belongs to the exponential family of distributions but is not of cannonical form;
(d) Belongs to the exponential family of distributions and is of cannonical form with natural parameter꞉ ;
Answer꞉
c). [3 marks] For the Negative binomial distribution ( is known)꞉ . Which of
the following statement(s) are true.
(a) Does not belong to the exponential family of distributions;
(b) Belongs to the exponential family of distributions and is of cannonical form with natural parameter꞉
;
(c) Belongs to the exponential family of distributions but is not of cannonical form;
(d) Belongs to the exponential family of distributions and is of cannonical form with natural parameter꞉