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Amy wishes to estimate the average diameter of screws produced by machine D. A sample of n screws produced by the machine was to be selected. Based on previously recorded data, the standard deviation of the diameter of screws produced by machine D was 1 . If she wants to ensure that at a 95% condence level of f0.05E(X]f+0.05 is obtained, determine the minimum number of observations, it that she needs to sample