Department of Economics
Professor Dale J. Poirier
University of California, Irvine
October 28, 2003
MIDTERM TEST
ECON 220A
Statistics and Econometrics I
(open book)
Directions
: You must answer each of the following questions. Points (out of 100) are allocated
as noted on the left. Allocate your time according to these points. To receive any partial credit, you
must
show your work.
1.
A gambler has in his pocket one fair coin and one two-headed coin.
(10)
(a)
He selects one of the coins at random, and when he flips it, it shows heads.
What is the probability that it is the fair coin?
(10)
(b)
Suppose that he flips the same coin a second time (independently of the
first flip and again it shows heads. Now what is the probability that it is the
fair coin?
(10)
(c)
Suppose that he flips the same coin a third time (Independently of the first

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