Abstract: Due to the problem of staffing in a call center with delay information， an optimized M/M/N+M queue algorithm with the performance measures of the customers’ behavior was proposed. Firstly， the estimation method of waiting time of delay information announced in the system was given， then the probability of customers’ behavior of abandonment including balking and reneging was formulated as a function of delay information. Secondly， some related performances were derived by applying the birthdeath process for steady state probability， and the fixed point algorithm was designed for the optimal staffing level. Lastly， the numerical study showed how delay information impacted on customer behavior and staffing. The numerical results indicated that the method proposed is of importance to human resource management.

Key words: call center, staffing, customer behavior, balking and reneging, delay information