Question 737156: To see whether people are keeping their car tires inflated to the correct level of 35 pounds per square inch (psi), a tire company manager selects a sample of 36 tires and checks the pressure. The mean of the sample is 33.5 psi, and the population standard deviation is 3 psi. Are the tires properly inflated? Use a=.10. Find the 90% confident interval of the mean. Do the results agree? Explain?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! To see whether people are keeping their car tires inflated to the correct level of 35 pounds per square inch (psi), a tire company manager selects a sample of 36 tires and checks the pressure.
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The mean of the sample is 33.5 psi, and the population standard deviation is 3 psi.
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Are the tires properly inflated? Use a=.10.
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Ho: u = 35
Ha: u # 35
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x-bar = 33.5
z(33.5) = (33.5-35)/[3/sqrt(36)] = -3
p-value = 2*P(z < -3) = 2*normalcdf(-100,-3) = 0.0027
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Since the p-value is less than 10%, reject Ho.
The test results do not support the tires being properly inflated.
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Find the 90% confident interval of the mean. Do the results agree?
Using my Ti-84 I get:
90% CI: (32.678,34.3220
Since 35 is not in the 90% confidence interval the test does not
support proper inflation at the 10% level of significance level.
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Cheers,
Stan H.
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