2
UNIT 3 TUTORIAL EXERCISES
1.
Among employed women, 25% have never been married. Select 12 employed women
at random.
(a)
The number in your sample who have never been married has a binomial
distribution. What are the binomial parameters
n
and
p
?
(b)
What is the probability that exactly 2 of the 12 women in your sample have never
been married?
(c)
What is the probability that 2 or fewer have never been married?
2.
A telemarketer is employed to telephone 10 households each evening between 6 and
7pm with a view to selling a particular service.
From past experience it is known that
the probability of any one household being interested in purchasing the service is
p
=
0.20.
Let the random variable
X
represent the number of households called on a given
evening that are interested in the service.
(a) Comment on the suitability of modelling the (relative frequency) distribution of
X
as a binomial distribution.
(b) Use the binomial distribution tables to calculate: P(
X
= 4), P(
X
< 4), P(
X
≥ 1).
3.
A believer in the “random walk” theory of stock markets thinks that an index of stock
prices has a probability of 0.65 of increasing in any one year. Let
X
be the number of
years among the next 5 years in which the index rises.
(a)
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 Three '08
 henry
 Normal Distribution, Standard Deviation, Probability theory, Cumulative distribution function, Internet access

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