The department manager of a local retail outlet found that after restructuring the sales department, by reducing the sales force costs, the costs had fallen.

Despite this the frontline sales representatives began to undertake support tasks like creating reports, tracking orders, and developing sales materials. This reduced the amount of time a representative could spend with customers. As a result, the outlet’s revenues decreased by an average of 3 clients per $1,000. To study this further, the manager selected a sample of 30 clients, which is shown as follows:

5 1 4 1 2 5 1 5 1 5 3 1 1 1 1 4 1 3 1 1 1 5 1 5 4 5 5 3 1 1 Determine the sampling error of this sample.