Question: Inside the Box Corporation makes corrugated cardboard boxes. The specification of One type of these boxes states that the breaking capacity of this box is 75 pounds. A sample of 53 randomly selected such boxes were loaded until they broke. The average breaking capacity of these boxes was found to be 78.92 pounds. Suppose that the standard deviation of the breaking capacities of all such boxes is 2.57 pounds. Calculate a 95 % confidence interval for the average breaking capacity of all boxes of this type.
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Answer: M = 78.92
Z = 1.96
S = ?(2.572/53) = 0.35

? = M ± Z(S)
? = 78.92 ± 1.96*0.35
? = 78.92 ± 0.6919
95% CI [78.2281, 79.6119]  Edit