Efficient manufacturing:Efficiency experts study the processes used to manufacture items in order to make them as efficient as possible. One of the steps used to manufacture a metal clamp involves the drilling of three holes. In a sample of

90

clamps, the mean time to complete this step was52.8

seconds. Assume that the population standard deviation is=

10

seconds. Round the critical value to no less than three decimal places.

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Part 1 of 2

(a) Construct a

99

%

confidence interval for the mean time needed to complete this step. Round the answer to at least one decimal place.A99

%

confidence interval for the mean is

<

<

.