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Stat 503
Homework #4 (80 points)
Due in class on TUESDAY 9/28
1. (13pts) In an agricultural experiment, a large uniform field was planted with a single variety of
wheat.
The field was divided into many plots (each plot being 7
100 ft) and the yield (lb.) of grain
was measured for each plot.
These plot yields followed approximately a normal distribution with
mean 88 lb. and standard deviation 7 lb.
What percentage of the plot yields were
(a)
(3pts)80 lb. or less?
(b)
(3pts)90 lb. or more?
(c)
(3pts)between 75 and 90 lb.?
(d)
(4pts)80lb. or less, with a condition given that the yield is between 75 and 90 lb.?
2. (13pts)The serum cholesterol levels of a certain population of boys follow a normal distribution
with mean 176 mg/dl and standard deviation 30 mg/dl.
What percentage of the boys have serum
cholesterol values
(a)
(3pts) more than 186?
(b)
(3pts)less than 156?
(c)
(3pts)between 121 and 156?
(d)
(4pts)between 121 and 156, but given the condition that we know the cholesterol value is less
than 156?
3.(6pts)For the serum cholesterol distribution of question5, find
(a)
(3pts)the 80
th
percentile
(b)
(3pts)the 20
th
percentile
4. (10 pts) The shell thicknesses of the eggs produced by a large flock of hens follow approximately a
normal distribution with mean equal to 0.38 mm and standard deviation equal to 0.03 mm.
(a)(3pts) Find the 95
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This note was uploaded on 09/26/2010 for the course STAT 503 taught by Professor Staff during the Fall '08 term at Purdue UniversityWest Lafayette.
 Fall '08
 Staff

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