4.4 Service Design Process
Service design is more comprehensive and occurs more often than product design.
The inherent variability of services processes requires that the service system be carefully designed.
Figure 4-3 (Tools for Service Design) shows the service design process beginning with a service concept and ending with service delivery.
4.4 Service Design Process
4.4 Service Design Process
There are many different tools for designing services. Quality function deployment (QFD), has wide application in services it is discussed in the next section. Other common tools are service blueprints, scripting, servicescapes, and waiting line analysis.
Waiting Line Analysis for Service Improvement:
Anyone who goes shopping, or to the post office experiences the inconvenience of waiting in line. Not only do people spend time waiting in lines, but machinery waits in line to be serviced or repaired, trucks line up to be loaded or unloaded at a shipping terminal, and planes wait to take off and land. Waiting takes place in virtually every productive process or service. Since the time spent by people and things waiting in line is a valuable resource, the reduction of waiting time is an important aspect of operations management.
Companies are able to reduce waiting time and provide faster service by increasing their service capacity, which usually means adding more servers – that is, more tellers, more mechanics, or more checkout clerks. However, increasing service capacity has a monetary cost, and therein lies the basis of waiting line, analysis: the trade-off between the cost of improved service and the cost of making customers wait.
4.4 Service Design Process
Waiting lines result because customers do not arrive at a constant, evenly paced rate, nor are they all served in an equal in an amount of time. Customers arrive at random times, and the time required to serve each individual is not the same. A waiting line is continually increasing and decreasing in length (and sometimes empty) but in the long run approaches an average length and waiting time.
Decisions about waiting lines and the management of waiting lines are based on these averages for customer arrivals and service times. They are used in queuing formula or models to compute operating characteristics (see: Table 4-1) such as the average number of customers waiting in line and the average time a customer must wait in line.
(1) Element of a waiting Line. (1) The calling population is the source of the customers to the waiting line system, and it can be either infinite or finite. (2) The arrival rate is the rate at which customers arrive at the service facility during a specific period. Arrivals per unit of time at a service facility can be frequently be described by a Poisson distribution. (3) Service times in a queuing process may also be any one of a large number of different probability distributions. The distribution most commonly assumed for service times is the negative exponential distribution.
(2) Basic waiting line structures. Waiting line processes are generally categorized into two basic structures: (1) Single-server waiting line. (2) Multiple-server waiting line.
4.4 Service Design Process
Table 4-1
Queuing System Operating Characteristics
| Notation |
Operating Characteristics |
| L |
Average number of customers in the system (waiting and being served) |
| Lq |
Average number of customers in the waiting line |
| W |
Average time a customer spends in the system (waiting and being served) |
| Wq |
Average time a customer spends waiting in line |
| Po |
Probability of no (i.e., zero) customers in the system |
| Pn |
Probability of n customer in the system |
| P |
Utilization rate, the proportion of the time the system is in use |
(3) Waiting line models. The simplest, most basic waiting line structure is the single –server model. We run into this type of waiting line every day.
The Basic Single- Server Model:
4.4 Service Design Process
4.4 Service Design Process
The probability of exactly n customers in the queuing system is

The average number of customers in the queuing system (i.e., the customers being served and in the waiting line) is

The average number of customers in the waiting line is

The average time a customer spends in the queuing system (i.e., waiting and being served is
4.4 Service Design Process
The average time a customer spends waiting in line to be served is

The probability that the server is busy and a customer has to wait, known as the utilization factor, is

The probability that the server is idle and a customer can be served is

Remember that these operating characteristics are averages that result over a period of time; they are not absolutes.
4.4 Service Design Process
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4.4 Service Design Process