A telephone customer service center wants to ensure that the majority of customer calls are answered within a reasonable amount of time. Based on customer feedback, the company has determined that this wait time is between 10 and 45 seconds. A large sample of data points collected reveal an average wait time of 31 seconds with a standard deviation of 4.5 seconds.
Calculate the process capability index AND advise if the process is at an acceptable level for an existing process (defend your answer). Please show all calculations.