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    Building confidence interval under either t or z distribution

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    Q4
    A system consists of five identical components connected in series as shown:

    As soon as one component fails, the entire system will fail. Suppose each component has a lifetime that is exponentially distributed with mean λ = 2 years and that component fail independently of one another.
    I. What is the probability that the first component is still working after 1 year?
    II. What is the probability that the entire system fails in 1 year?

    Q5
    The monthly starting salaries of students who receive an MBA degree have a standard deviation of $70. What sample size should be selected so that there is a 95% confidence of estimating the mean monthly within a sampling error of $ 18 or less?

    Q6
    The compressive strength of a concrete is being used by an engineer and the results were recorded as follows:
    221, 222, 231, 223, 230, 215, 210
    Construct a 95% confidence interval on the mean strength.

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    Solution Summary

    The solution gives detailed steps on finding the probability and building confidence interval under either t or z distribution.

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