SOLUTION: Managers at an automobile manufacturing plant would like to estimate the mean completion time of an assembly line operation, . The managers plan to choose a random sample of comple

Question 1176934: Managers at an automobile manufacturing plant would like to estimate the mean completion time of an assembly line operation, . The managers plan to choose a random sample of completion times and estimate via the sample. Assuming that the standard deviation of the population of completion times is 10.2 minutes, what is the minimum sample size needed for the managers to be 90% confident that their estimate is within 2.0 minutes of ?
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
start with half-interval, which is z*sigma/sqrt(n), and for 90% CI z=1.645
so 1.645*10.2/sqrt(n)=2
and sqrt(n)=1.645*10.2/2
=8.3895
so n=70.38 or 71
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