The Financial Director (FD) of your company has heard it said that 80% of profits come from 20% of customers. The FD has accused the sales team of wasting time on serving customers who are not valuable to the business.

 The FD has instructed you to take a random sample of 100 customers and to calculate the total contribution the company earned from each customer in the past year. The FD intends to instruct the sales team to stop selling to the bottom 25% of these customers in order to improve profitability.

Which THREE of the following factors should the FD consider when he interprets your results?