BUAD 310: Quiz 3
First name: …………….…….….
.
Last name:…………….…….….
.
Use the following to answer questions 1 and 2:
An assembly plant orders a large shipment of electronic circuits each month.
The supplier claims that the population proportion
of defective circuits is
=.04.
When a shipment arrives, the plant manager selects a random sample of 300 circuits that are
tested and the sample proportion of defective circuits is computed.
This result is used for a hypothesis test to determine if there
is sufficient evidence to conclude that the population proportion of defectives circuits from this supplier is greater than .04.
The hypotheses are:
H
o
:
± ²³´
and H
a
:
µ ²³´
.
1.
For a level of significance of α=.025, what value does the sample proportion need to exceed in order for the manager to
conclude that
µ ²³´
?
(a)
.049
(b)
.040
(c)
.062
(d)
.041
(e)
.065
2.
In a sample of 300 circuits, the manager found 21 that were defective.
Determine the pvalue associated with the test
statistic for the test described above.
(a)
.07
(b)
.0040
(c)
.0207
(d)
.9960
(e)
.4721
Use the following to answer questions 3 and 4:
A manufacturer of light bulbs is considering a change in their supplier of tungsten for use in the bulbs’ filaments.
They believe
this will result in bulbs that are “longer lasting”.
Currently, the lifetime, X, of their bulbs is a normally distributed random
variable with population mean μ=750 hours.
After using tungsten from the new supplier for a production run, a random sample
of 25 bulbs will be selected and the average lifetime of the bulbs will be computed.
This result will be used to determine if there
is sufficient evidence to conclude that the population mean lifetime of bulbs using this supplier is greater than 750 hours. The
hypotheses are:
H
o
:
μ ≤ 750 and H
a
: μ > 750.
3.
The results of the sample showed an average lifetime of 753.3 hours with a sample standard deviation of 7.5 hours.
Which of
the following statements is true?
(Choose the most appropriate response.)
(a)
The null hypothesis should be rejected for a level of significance of α=.01.
(b)
The pvalue of the test statistic is less than .025.
(c)
The pvalue of the test statistic is greater than .05.
(d)
The null hypothesis should not be rejected for a level of significance of α=.05.
(e)
Both statements (c) and (d) are true.
4.
The production manager is concerned about the size of the sample used for the test.
He decides to use a random sample of
100 bulbs using the new supplier’s material and repeat the test described above with a level of significance of α=.025.
If it is
true that using the new supplier results in bulbs that have a population mean lifetime of μ=753.12 hours and standard deviation
σ=7.5 hours, which of the following statements is true?
(Choose the most appropriate response.)
(a)
The new sample will result in the conclusion to reject H
o
because it is false.
(b)
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 Spring '07
 Lv
 Business, Null hypothesis, Statistical hypothesis testing

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