A plant manager wishes to determine the difference in number of accidents per day between two departments. She wants to be 90% certain of the difference in daily averages to within 0.25 accidents per day. Assume standard deviations of 0.8 and 0.5 accidents per day in the two departments, respectively. What should be used to determine how many days' (n) records should be examined?
Added by Harizz K.
Step 1
Since the two departments are independent, the variance of the difference is the sum of the variances, so the standard deviation of the difference is the square root of the sum of the squares of the standard deviations, which is sqrt(0.8^2 + 0.5^2) = 0.943. Show more…
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