Question 3

The Customs authorities at Gaborone Airport claim that imported cow feed is cleared within an average of 72 hours of the goods being offloaded from the plane. However local farmers are not convinced of this and want to test this claim. They analyzed documents of 46 recent shipments and found that the average clearance time was 75.9 hours. Assume a population standard deviation of 18 hours and that clearance time is approximately normally distributed.

Assuming a significance level of 0.05%, test the claim of the customs authorities and conclude. [5]