A confidence interval for a population mean has a margin of error of 3.1.
a)Determine the length of the confidence interval.
b)If the sample mean is 56.7, obtain the confidence interval.

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  1. a)

    ± 3.1


    56.7 - 3.1 = 53.6
    56.7 + 3.1 = 59.8

    Interval is 53.6 to 59.8

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  2. the population of 1500 construction truck has load distributed normally with the mean of 6 tons and the standard deviation of 1 ton. Find the probability that its load is greater than 7?

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