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Assignment
3
NOTICE:
1.
All assignments should be submitted in hard copies to the collection box
2.
The
due date
for 3
rd
assignment is
Nov 20,
2:00 pm
.
Late HWs are
NOT
accepted.
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Problem1.
A production process for steel rods used to reinforce concrete is known to
produce rods whose length have a variance of 64 cm. The production machinery has been
set to produce rods with a mean of 600 cm in length. These rods are tied into bundles of
40 for shipment to construction sites.
a. What is the probability that the average length of a randomly selected bundle is less
than 598 cm?
b. What is the probability that the average length of a randomly selected bundle is less
than 598 cm or more than 601 cm?
c. Under what assumptions are the probabilities found in parts (a) and (b) valid?
d. If the bundle size is 25 rather than 40, what additional assumption is necessary in order
to use the sampling distribution of
sample mean
e. Suppose that the bundle size is 25. What is the probability of selecting a bundle that
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 Spring '09
 AnthonyChan

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