T the length of time we observed the system

A the number of request arrivals we observed

C the number of request completions we observed

Workload intensity/arrival rate Lamda the rate at which the customers arrive (eg 0.5 customers/second) Lamda = A/T

Throughput X the rate at which customers pass through the service center (0.5 customers/second) X = C/T

N the average number of requests in the system (customer population) N = W/T

Residence time R the average time spent at the service center by a customer, both queueing and receiving service R=W/C

Queue length the average number of customers at the service center both waiting and receiving service (1.67 customers)

B the length of time that the resource was obeserved to be busy

Utilization U the proportion of time the server is busy (eg 0.625/62.5%) U = B/T

S the average service requirement of a customer (eg 1.25 seconds) S = B/C

Z think time of a terminal user

Dk Service demand at resource k Dk=VkSk

BASIC LAWS