A machine makes catheters for use in heart tests. The machine is adjusted to mak
ID: 3155205 • Letter: A
Question
A machine makes catheters for use in heart tests. The machine is adjusted to make catheters of diameter 2 mm. Production records show that when the machine is so adjusted, it will make catheters with population mean diameter 2 mm and with population standard deviation .05 mm. During production, an inspector checks the diameters of catheters to see if the machine has slipped out of adjustment. A random sample of 50 catheters is taken. If the mean diameter for this sample is 2.05 mm, does this indicate that the machine has slipped out of adjustment and the average diameter of the catheters is no longer mu = 2 mm? The best test to use in this situation is a:
z-test.
t-test.
2-sample t-test.
1-proportion z-test.
For years, the Brite Lite Company has made light bulbs that have had an average lifespan of 800 hours of use. Recently, some changes were made in the design and the production of the light bulbs. It is thought that the lifespan of the light bulbs has been increased by the changes. A random sample of 55 new light bulbs is selected and tested. The sample average bulb life is 910 hours with sample standard deviation 126 hours. Does this indicate that the population mean bulb life has increased? The correct hypothses for this test are
HO: mu = 800
HA: mu = 910
HO: mu = 800
HA: mu > 800
HO: mu = 800
HA: mu < 800
HO: mu = 910
HA: mu = 800
z-test.
t-test.
2-sample t-test.
1-proportion z-test.
For years, the Brite Lite Company has made light bulbs that have had an average lifespan of 800 hours of use. Recently, some changes were made in the design and the production of the light bulbs. It is thought that the lifespan of the light bulbs has been increased by the changes. A random sample of 55 new light bulbs is selected and tested. The sample average bulb life is 910 hours with sample standard deviation 126 hours. Does this indicate that the population mean bulb life has increased? The correct hypothses for this test are
HO: mu = 800
HA: mu = 910
HO: mu = 800
HA: mu > 800
HO: mu = 800
HA: mu < 800
HO: mu = 910
HA: mu = 800
Explanation / Answer
Z test (population standard deviation is known).
The hypothesis test is to check the claim, whether the mean life span of light bulb shas increased by the change. This account sfor right tailed alternative hypothesis.
H0:mu=800
H1:mu>800
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