Operations managers must ensure products are manufactured and delivered on time, on budget, and to specifications. How can managers be sure all will go smoothly and be completed by the required time? One popular technique for monitoring the progress of production was developed in the 1950s for constructing nuclear submarines: the program evaluation and review technique (P ERT). PERT users analyze the tasks to complete a given project, estimate the time needed to complete each task, and compute the minimum time needed to complete the whole project. The steps used in PERT are (1) analyzing and sequencing tasks that need to be done. (2) estimating the time needed to complete each task. (3) drawing a PERT network illustrating the information from steps 1 and 2, and (4) identifying the critical path. The cri tical path is the sequence of tasks that takes the longest time to complete. We use the word critical because a delay anywhere along this path will cause the project or production run to be late. Figure 9.3 illustrates a PERT chart for producing a music video. The squares indicate completed tasks, and the arrows indicate the time needed to complete each. The path from one completed task to another illustrates the relationships among tasks; the arrow from "set designed" to "set materials purchased" indicates we must design the set before we can purchase the materials. The critical path, indicated by the bold black arrows, shows producing the set takes more time than auditioning dancers, choreographing dances, or designing and making costumes. The project manager now knows it's critical that set construction remain on schedule if the project is to be completed on time, but short delays in dance and costume preparation are unlikely to delay it. FIGURE 9.3 PERT CHART FOR A MUSIC VIDEO The minimum amount of time it will take to produce this video is 15 weeks. To get that number, you add the week it takes to pick a star and a song to the four weeks to design a set, the two weeks to purchase set materials, the six weeks to construct the set, the week of rehearsals, and the final week when the video is made. That's the critical path. Any delay in that process will delay the final video.