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Unformatted text preview: dents are selected at
random, what is the probability that at least 8 students possess credit cards?
6. At a tram stop, the waiting times of a tram are normally distributed with a mean of 10 minutes and a standard
deviation of 3 minutes. What proportion of passengers have to wait more than 2 minutes but less than 7
minutes?
7. Suppose that 70% of residents in a city possess mobile phones. A random sample of 60 residents is selected
from the population. What is the probability that the number of residents possesing mobile phones in the
sample will be between 45 and 50 inclusive?
8. The number of accidents per month at a certain traﬃc black spot follows poisson distribution. Statistics show
that on average there are 48 accidents per year. What is the probability that more than 2 accidents will occur
in a month? 2...
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This note was uploaded on 08/26/2013 for the course STAT 0302 taught by Professor Guo during the Spring '12 term at HKU.
 Spring '12
 guo
 Statistics, Variance

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