Question 1
A random sample of 64 students at a university showed an average age of 25 years and a sample standard deviation of 2 years. The 98% confidence interval for the true average age of all students in the university is
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20.5 to 26.5
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24.4 to 25.6
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23.0 to 27.0
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20.0 to 30.0
Question 2
A sample of 20 items from a population with an unknown σ is selected in order to develop an interval estimate of μ. Which of the following is not necessary?
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We must assume the population has a normal distribution.
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We must use a t distribution.
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Sample standard deviation must be used to estimate σ.
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The sample must have a normal distribution.