Question 1193182
Best point estimate is from the sample, 7.2 jobs
95% half-interval is z(0.975)*sigma/sqrt(n)
=1.96*2.1/sqrt(50)
=0.58 hours
interval is (6.62, 7.78) hours 
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half-interval is 2.576*2.1/sqrt(50)
=0.765 hours
(6.43, 7.97) hours