Book PS #9
6.20 (page 370)
To clarify the question, the population standard deviation σ = $220.
Round your answers to four
decimal places.
Also answer this question:
How large a sample of onebedroom apartments in Exercise 6.20 would be need to estimate the
mean μ within
±
$50 with 99% confidence?
Remember to express your answer as a whole
number.
6.32 (page 371)
a) Round your answers to four decimal places.
b) Remember to express your answer as a whole number.
#1) The mean yield of corn in the US is about 120 bushels per acre.
A survey of 40 farmers this
year gives a sample mean yield of
x
= 123.8 bushels per acre.
We want to know whether this is
good evidence that the national mean this year is not 120 bushels per acre.
Assume that the
farmers surveyed are an SRS from the population of all commercial corn growers and that the
standard deviation of the yield in this population is σ = 10 bushels per acre.
We want to test:
H
0
:
μ = 120
H
a
:
μ
≠
120
Give the z test statistic and its Pvalue.
Round your answers to four decimal places.
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 Fall '08
 ABDUS,S.
 Statistics, Standard Deviation, $50, decimal places

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