Glossary

This glossary lists some common terms that are used for the analysis of waiting lines in different contexts, and the corresponding terms used in the Queueing ToolPak.

• AHT = Average Handling Time: The average time to serve a customer. Equals one divided by the service rate.
• AHT = Average Holding Time on Trunks: The average time a customer spends in the system, in a telecommunications context (trunk = telephone line). Use the QTPMMS_W function to calculate this. Note that this term has the same acronym as Average Handling Time, but a different meaning.
• ASA = Average Speed of Answer: The average time a customer waits before being answered, i.e., the average time he or she waits in line. Use the QTPMMS_Wq function to calculate this.
• ATB = All Trunks Busy: A situation where the system is filled to capacity, so that no new customers can enter the system. Used in telecommunications. Use the QTPMMS_PrFull function to calculate the probability of this occurring.
• TSF = Telephone Service Factor: Same as QTPMMS_ServiceLevel.
• Average Delay: Average waiting time in queue. Use the QTPMMS_Wq function to calculate this.
• Average Delay of Delayed Calls: Average waiting time in queue, for those customers that actually waited. Use QTPMMS_Wq / QTPMMS_PrWait to calculate this.
• Call Load: Equals the arrival rate times the average service time, or the arrival rate divided by the service rate. Measures the average amount of work, measured in time units, that is coming into the system per time unit.
• Erlang B, or Erlang's loss formula: This formula calculates the probability that a caller will get a busy signal when calling a system where the number of agents equals the number of telephone lines (trunks). The QTPMMS_PrFull function, with Queue Capacity set equal to zero, calculates this quantity.
• Erlang C formula: This formula calculates the probability that no server is available in a system with infinite queue capacity. Use the QTPMMS_PrWait function, with Queue Capacity omitted or set equal to "Inf," to calculate this quantity.
• GoS = Grade of service: The probability that all lines are busy, in a telecommunications context. Use the QTPMMS_PrFull function to calculate this.
• Occupancy: This is the same as server utilization.

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