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Read Class Notes 12, first three pages.
Study Class 3 example exercise.
HW3
Bus Issue:
Financial service professionals monthly sales
BusQues:
Is the mean sales/month less than $80,000? (Do we have evidence to conclude the population mean is less than 80?)
Data:
Sample of 100.
Assume population (all fin serv professionals) stdev = 12($1000). Two cases: (a.) xbar = 78.5.
(b.) xbar = 77.
Analysis:
Hypothesis Testing  Normal Test for Mean
1. Hypotheses:
Could draw the Normal sampling distribution of xbar:
2. Test Statistic:
xbar
f(xbar)
75.0
0.000
3. Sign Level:
75.5
0.000
4. Reject Rule:
Reject Ho if xbar <
77.21
=NORMINV(.01,80,12/10)
76.0
0.001
12a
12b
76.5
0.005
5. Calculations:
xbar =
78.5
77
77.0
0.015
pvalue =
0.106
0.006
=NORMDIST(77,80,12/10,TRUE)
77.5
0.038
78.0
0.083
6. Conclusion:
Do not reject Ho.
Reject Ho.
78.5
0.152
79.0
0.235
Bus Answer:
This sample (mean=$78,500)
This sample (mean=$77,000) is strong
79.5
0.305
is insufficient evidence to con
enough evidence to conclude that the
80.0
0.332
clude that the mean monthly
mean monthly sales is less than $80,000.
80.5
0.305
sales is < $80,000.
(If the mean were exactly = 80,
81.0
0.235
(If the mean exactly = 80,
the likelihood for a sample
81.5
0.152
the likelihood for a sample
of 100 of obtaining this
82.0
0.083
of 100 of obtaining this
sample mean or smaller
82.5
0.038
sample mean or smaller
is less han 1%. )
83.0
0.015
is more than 10%.
In this
83.5
0.005
test, we used a "cutoff" of 1%)
84.0
0.001
of 1%.)
84.5
0.000
85.0
0.000
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This note was uploaded on 07/17/2011 for the course STATS 211 taught by Professor Dunne during the Spring '07 term at University of Dayton.
 Spring '07
 Dunne

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