The manager of an accounting office is studying the problem of incorrect account numbers being entered into the computer system and wishes to produce a p chart. A subgroup of 200 account numbers is selected from each day's entries and checked to determine the number of incorrect entries. The average proportion of such incorrect entries for the last several months is 0.12.

(a) Calculate the control limits for this process.

(b) After the control limits are calculated and drawn on the control chart and the proportions are plotted for every day what are the signals that indicate that something has gone