1
The University of Hong Kong
Department of Statistics and Actuarial Science
STAT0302 Business Statistics
Semester 2 2009/2010
Example Class 9 Question
1.
40 similar machines, each using 16 components which perform the same function but
wear independently of each other, were examined after 30 days of continuous running.
The following numbers of worn components were recorded:
8
7
5
8
8
6
8
1
4
3
2
8
5
5
6
7
0
5
3
8
7
5
7
4
5
6
9
1
4
4
6
3
4
8
2
8
4
5
10
5
(a)
Obtain an unbiased estimate of
p
, the probability that a component is worn after
a period of 30 days.
(b)
Construct a 90% confidence interval for
p
.
(c)
How many more machines are required for a further similar experiment if the
maximum estimation error, based on the combined information of the two
experiments, is desired to be 2 percentage points, with 0.95 probability?
2.
200 Turnip seeds (120 of variety
A
and 80 of variety
B
) were sown and kept under
identical laboratory conditions for three weeks. At the end of this period it was found
that 90 seeds of
A
and 54 seeds of
B
had germinated.
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 Spring '09
 Prof.Chiu
 Statistics, 10%, 30 days, 3 years, University of Hong Kong Department of Statistics

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