5. The mean life of light bulbs produced by the Brite Light Bulb Company is 950 hours with a standard deviation of 225 hours. Assume that the population is normally distributed. Suppose you take a random sample of 12 light bulbs.
(a) What is the mean of the sample mean life?
(b) What is the standard deviation of the sample mean?
6. A population has a variance σ2 of 81. A sample of 25 from this population had a mean equal to 17. Can we reject H0: μ = 20 in favor of H1: μ ≠ 20? Let α = 0.05.

 

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