PAM 210 Lecture 1
Problem Set #8
Posted: Monday, 7
th
of April, 2008
Due: Monday, 14
th
of April, 2008
#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 value and its Pvalue. Round your zvalue to two decimal places and its Pvalue to four
decimal places, if necessary.
Do you reject H
0
at the 5% level?
Ans.(25 points total)
4
.
2
4033
.
2
40
/
10
120
8
.
123
/
0
≈
=

=

=
n
x
z
σ
μ
.
(8 points)
Since this a twosided test (since the alternative hypothesis is twosided), therefore the Pvalue is
=
)
4
.
2
(
*
2
)

(
*
2
≥
=
≥
Z
P
z
Z
P
From table A,
0082
.
9918
.
1
)
4
.
2
(
=

=
≥
Z
P
So the Pvalue= 2*.0082=.0164
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '08
 ABDUS,S.
 Statistics, Normal Distribution, Standard Deviation, Statistical hypothesis testing, decimal places

Click to edit the document details