ISMT111 Problem Set #5
(1)
It is known that the service life of a particular automotive part is normally distributed.
If
92.51% of the parts have service lives greater than 2160 hours and 3.92% have service lives
greater than 17040 hours, what are the mean
μ
and standard deviation
σ
of the distribution
of service life of this particular part?
(2)
Suppose GMAT (Graduate Management Admissions Test) scores are normally distributed
with a mean
μ
= 500 and a standard deviation
σ
= 100 . Compute the interquartile range
for this distribution, i.e., the distance between the 75th and 25th percentile of the distribution
of GMAT scores.
(3)
A customer service desk receives an average of five customers per hour.
Assume that the
number of customers arriving per hour is Poisson distributed. What is the probability that at
least 10 people will request service in a particular twohour period?
(4)
A machine is used to regulate the amount of additive QQX in gasoline.
It can be set to
discharge, on the average,
μ
milliliters of additive QQX per liter of gasoline. It is also known
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 Fall '09
 AnthonyChan

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