The manager of a retail sales branch of a brokerage office is concerned with the number of undesirable trades made by the sales staff. A trade is considered undesirable if there is an error on the trade ticket. Trades that are in error must to be cancelled and resubmitted. The cost of correcting errors is billed to the brokerage. In studying the problem, the manager wants to know whether the proportion of undesirable trades is in a state of statistical control so he can plan the next step in a quality improvement process. Data are collected for a 30-day period and present in the excel sheet.

Construct an appropriate control chart for these data.

Is the process in a state of statistical control? If not, on which days is it out of control?