LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
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M.Sc. DEGREE EXAMINATION – STATISTICS
FIRST SEMESTER – APRIL 2007
ST 1810 / 1803 – ADVANCED DISTRIBUTION THEORY
Date & Time: 30/04/2007 / 1:00 – 4:00 Dept. No. Max. : 100 Marks
SECTION – A Answer all the questions (10 x 2 = 20)
- Define truncated Poisson distribution and find its mean.
- Show that the minimum of two independent exponential random variables is exponential.
- Define bivariate Poisson distribution.
- If (X1,X 2) is bivariate binomial, find the pgf of X1+X 2.
- If (X1,X 2) is bivariate normal, find the distribution of 2X1 -3 X 2 .
- Find the marginal distributions associated with a bivariate exponential distribution of
Marshall – Olkin.
- Find the mean of non-central t – distribution.
- Let X (1) ,X(2 ),X (3) be order statistics from exponential distribution.Find E{X (3) – X(1)}.
- Let X 1 ,X2 ,X 3 be independent N(0,1) random variables. Examine whether
2X12 + X2 2 + 2X3 2 – X1X3 + 2X2X3 has a chi-square distribution.
- Let X 1 ,X2 be independent N(0,1) random variables. Find the MGF of 2X1X2.
SECTION – B Answer any five questions (5 x 8 = 40)
- State and establish the mgf of a Power series distribution.Deduce the mgf of Binomial.
- For an Inverse Gaussian distribution,derive the cumulants. Hence find the mean and variance.
- State and establish the additive property for bivariate Poisson distribution.
- Derive the conditional distributions associated with bivariate binomial distribution.
- Let X = (X1,X2)/ be such that every linear combination of X1and X2 is distributed as normal.
Show that X is bivariate normal.
- If X = (X1,X 2)/ is bivariate exponential(l1, l2, l3), show that X1 and X 2 are independent if and only
if l3 = 0.
- Define non – central chi-square distribution and derive its probability density function.
- If X1, X2,X3,X4 are independent N(0 ,1) variables, examine whether X1+ 2X2 -X3 +3X4 is
independent of (X1– X2)2 + (X3 -X4)2 + (X1 – X3)2.
SECTION – C Answer any two questions (2 x 20 = 40)
19 a) State and establish a characterization of geometric distribution.
- b) Let X1, X2, …,Xn denote a random sample from lognormal distribution. Show that
the sample geometric mean is lognormal.
20 a) Define trinomial distribution. State and establish its additive property.
- b) If (X1,X 2)/ is bivariate normal with correlation coefficient r , show that the correlation coefficient
between X12 and X22 is r2.
21 a) Define non-central F distribution and derive its pdf .
- b) Discuss any two applications of non-central F distribution.
22 a) Let X1, X2, …,Xn be independent N(0,1) variables.State and establish a necessary and sufficient
condition for X/AX to be distributed as chi-square,where X =(X1,X2,…,Xn)/ .
- b) Explain compound distribution with an illustration
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