Sensitivity analysis helps to test the sensitivity of the optimum solution with respect to changes of the coefficients in the objective function, coefficients in the constraints inequalities, or the constant terms in the constraints.

For Example in the case study discussed:

The actual selling prices (or market values) of the two products may vary from time to time. Over what ranges can these prices change without affecting the optimality of the present solution?

Will the present solution remain the optimum solution if the amount of raw materials, production time, or storage space is suddenly changed because of shortages, machine failures, or other events?

The amount of each type of resources needed to produce one unit of each type of product can be either increased or decreased slightly. Will such changes affect the optimal solution ?

The Input or Arrival Process

•The input process is usually called the arrival process.

•Arrivals are called customers.

•We assume that no more than one arrival can occur at a given instant.

•If more than one arrival can occur at a given instant, we say that bulk arrivals are allowed.

•Models in which arrivals are drawn from a small population are called finite source models.

•If a customer arrives but fails to enter the system, we say that the customer has balked

The Output or Service Process

•To describe the output process of a queuing system, we usually specify a probability distribution – the service time distribution – which governs a customer’s service time.

•We study two arrangements of servers: servers in parallel and servers in series.

•Servers are in parallel if all servers provide the same type of service and a customer needs only pass through one server to complete service.

•Servers are in series if a customer must pass through several servers before completing service.

Queue Discipline

•The queue discipline describes the method used to determine the order in which customers are served.

•The most common queue discipline is the FCFS discipline (first come, first served), in which customers are served in the order of their arrival.

•Under the LCFS discipline (last come, first served), the most recent arrivals are the first to enter service.

•If the next customer to enter service is randomly chosen from those customers waiting for service it is referred to as the SIRO discipline (service in random order).

•Finally we consider priority queuing disciplines.

•A priority discipline classifies each arrival into one of several categories.

•Each category is then given a priority level, and within each priority level, customers enter service on a FCFS basis.