Question 5

1. Distinguish between a point estimate and confidence interval [5]

2. The operations manager of a PPC cement in Francistown 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 PPC customers. [5]

(b) Estimate a 95% confidence interval for the mean size of orders [ 5]

(c) Estimate a 80% confidence interval for the mean size of orders [5]