Question 185674
Can someone please help me solve this? thank you so much 
Managers at an automobile manufacturing plant would like to estimate the mean completion time of an assembly line operation, u. The managers plan to choose a random sample of completion times and estimate u via the sample. Assuming that the standard deviation of the population of completion times is 12.3 minutes, what is the minimum sample size needed for the managers to be 95% confident that their estimate is within 1.5 minutes of u? 
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Use the formula E = z*[s/sqrt(n)} and solve for "n":
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1.5 = 1.96[12.3/sqrt(n)]
sqrt(n) = 1.96*12.3/1.5] = 16.07
n = 258.31
Rounding up you get n = 259
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Cheers,
Stan H.