In the above call centre, if the mean call length changes to 3.2 minutes and the standard deviation to 0.9 minutes, how does this affect the C_p and C_pk? Do you think this is an appropriate way for the bank to monitor its call centre performance?

A call centre for a bank answers customers’ queries about their loan arrangements. All calls are automatically timed by the call centre’s information system and the mean and standard deviation of call lengths is monitored periodically. The bank decided that only on very rare occasions should calls be less than 0.5 minutes because customers would think this was impolite even if the query was so simple that it could be answered in this time. Also, the bank reckoned that it was unlikely that any query should ever take more than 7 minutes to answer satisfactorily. The figures for last week’s calls show that the mean of all call lengths was 3.02 minutes and the standard