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Unformatted text preview: Class Test 2 : Solution DATE: 2010 Instructor: Simin Seury Faculty of Liberal Arts & Professional Studies York University
AP/ECON 2500 3.0: Introductory Statistics for Economists I
Please note: the following only provides a brief guide. Your answer in exam is supposed to
include all steps (formula/calculation etc.) and explanation. Q1. The mailing list of a company that is planning to launch customer survey for one of their new
product that works as a diet supplement contains 60 percent nonsmokers and 40 percent
smokers. The company calls 30 people chosen at random from the list.
(a) Calculate the probability of having 20 nonsmoker out of the 30 people using Binomial
Probability formula:
M has a binomial distribution with n = 30 and p = 0.6. 30 20
10
So P(M = 20) = (0.6) (0.4) = 0.1152. 20 (b) What is the probability that the first smoker is reached on the fourth call?
P(1st woman is the 4th call) = (0.6)3(0.4) = 0.0864
(c) Instead of reaching people from their mailing list, the company decides to do a door to door
survey in Toronto. It is known that Toronto, with a population of 2.48 million people, is a
multicultural city and the approximately 22% people in this city are born outside Canada.
The statistician hired for this job chooses an SRS of 1000 residents for a sample survey and
wants to find the probability that 250 or more of the people in this sample were born outside
Canada. Can s/he use the Normal approximation for the sampling distribution of a sample
proportion to answer this question? Justify your answer.
As a rule of thumb, the population of Toronto is much larger than 10 times the sample size n =
1000. So we can use the usual formula for the standard deviation of ˆ p. ...
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 Spring '10
 SiminSeruy

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