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þÿAt the most aggregate level, a process can be thought of as a black box that uses resources (labor and capital)
to transform inputs (undiagnosed patients, raw materials, unserved cus- tomers) into outputs (diagnosed
patients, finished goods, served customers). This is shown in Figure 2.6. Chapter 3 explains the details of
constructing figures like Figure 2.6, which are called process flow diagrams. When analyzing the processes that
lead to the supply of goods and services, we first define our unit of analysis.
In the case of the interventional radiology unit, we choose patients as our flow unit. Choosing the flow unit is
typically determined by the type of product or service the supply process is dealing with; for example, vehicles
in an auto plant, travelers for an airline, or gallons of beer in a brewery.
As suggested by the term, flow units flow through the process, starting as input and later leaving the process as
output. With the appropriate flow unit defined, we next can evaluate a process based on three fundamental
process performance measures:
þÿ " The number of flow units contained within the process is called the inventory (in a production setting, it is
referred to as work-in-process, WIP). Given that our focus is not only on production processes, inventory could
take the form of the number of insurance claims or the number of tax returns at the IRS. There are various
reasons why we find inventory in processes, which we discuss in greater detail below. While many of us might
initially feel uncomfortable with the wording, the inventory in the case of the interven- tional radiology unit is a
group of patients.
þÿ " Thetimeittakesaflowunittogetthroughtheprocessiscalledtheflowtime.Theflow time takes into account that the
item (flow unit) may have to wait to be processed because there are other flow units (inventory) in the process
potentially competing for the same resources. Flow time is an especially important performance metric in
service environments or in other business situations that are sensitive to delays, such as make-to-order
production, where the production of the process only begins upon the arrival of the customer order. In a
radiology unit, flow time is something that patients are likely to care about: it measures the time from their
arrival at the interventional radiology unit to the time patients can go home or return to their hospital unit.
ext ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type
specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining
essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem
Ipsum
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Proposed study plan