The operations manager of a sugar mill in Durban wants to estimate the average size of an order received. An order is measured in the number of pallets shipped. A random sample of 87 orders from customers had a sample mean value of 131.6 pallets. Assume that the population standard deviation is 25 pallets and that order size is normally distributed.
(a) Estimate, with 90% confidence, the mean size of orders received from all the mill's customers. (Use the z-table.)
(b) Compute (a) using Excel's NORMSINV formula to find the z-value.
(c) Use Excel's CONFIDENCE formula to reproduce the findings in (a).
(d) If the sugar mill receives 720 orders this year, calculate, with 90% confidence, the total number of pallets of sugar that they will ship during the year.