## Info

Figures 17-7 and 17-8, five people entered the store within one minute of previous customers. The five customers may have come at the same time or different times. Likewise, 18 people entered within 16 minutes of other customers. The service rates are handled in the same manner. Fifteen people required 14 minutes of service and 20 people required 18 minutes of service.

The second step transforms the arrival and service histograms into a step-function type chart in which for every number there corresponds one and only one arrival and service rate. To develop these charts, it is best to have 100 observances for both arrivals and services, as discussed in the first step and shown in Table 17-9.

The step-function charts are based upon 100 numbers. Consider the service data in Table 17-9. We let the numbers 1 through 5 represent 10 minutes of service since there were 5 observations. Ten observations were tabulated for 12 minutes of service. This is represented by the numbers 6 through 15. Likewise, the numbers 16 through 30 represent the 15 observations of 14 minutes of service. The remaining data can be tabulated in the same manner to complete the service chart. The service step-function chart is shown in Figure 17-9 and the arrival step-function chart is shown in Figure 17-10. Some points on these charts are plateau points, as the number 15 on the service chart. The number 15 refers to the left-hand-most point. Therefore, 15 implies 12 minutes of service, not 14 minutes of service.

The third step requires the generation of random numbers and the analysis. (See Table 17-10.) The random numbers can be obtained either from random number tables or from computer programs that contain random number generators. These random numbers are used to simulate the arrival and service rates of customers from the step-function charts in Figures 17-9 and 17-10. Random numbers are generated between 0 and 1. However, it is common practice to multiply these numbers by 100 so as to have integers between 0 and 99 or 1 and 100. As an example, consider the following 10 random numbers: 1, 8, 32, 1, 4,15, 53, 80, 68, and 82. The numbers are read in groups of two, with the first number representing arrivals and the second representing service. From Figure 17-10, the number 1 corresponds to a 0 arrival rate. From Figure 17-9, the number 8 corresponds to 12 minutes