There exists too much uncertainty regarding the duration of completing various activities. This uncertainty makes planning very important. Project planning is a process of stating how an activity that has defined stages is to be completed within certain timeframes. This process involves estimating, resourcing, and planning (Harold, 2003). The three need to take place in parallel as they are closely interrelated. Planning involves defining the work to be completed. Estimation involves calculation of the effort and time required per portion of the job. Resourcing involves allocating the actual resources in the plan. To set the exact deadlines for undertakings like research and development is difficult, and therefore in most case, only the probable deadline is given. For each of the activities in a project, we can set: the Optimistic duration estimate which is the estimated minimum time required for an activity, the most probable time estimate which is the estimated normal time for an activity, and pessimistic duration estimate which gives the estimated maximum time for an activity (Fleming, 2005). The three estimations are related and are considered when coming up with a specified duration for all activities in a project.
Before any project work begins, there needs to be an accurate and advanced time estimate. Inaccurate time estimates usually results in incomplete projects. Developing estimates is complex especially when the project is a huge one and has numerous stakeholders. Therefore, developers employ varied techniques during a project’s estimation phase in an effort to make the estimates more accurate (Filicetti et al, 2009). Among these methods is PERT which has been proven to be very successful. Others include CPM, Top Down Estimating, WAVE, and Function Point Counting. PERT was developed in 1950s by the American Navy for their Ballistic Missiles program which involved numerous contractors. The PERT methodology enabled successful completion of the project two years ahead of schedule.
Success of PERT Method
PERT is all about management and it involves several statistical methods too. The methodology helps in breaking down chores into more detailed activities such that after the Gantt chart is prepared, the interdependencies among these activities are clearly illustrated. PERT method uses statistics to derive the estimates. There are several advantages of using the PERT methodology during project development, and these advantages are what help to inflate a project. The advantages include the reduction of project risks as it helps to identify the critical paths, more effective scheduling through the clear definition of dependencies, more flexibility in alteration of project development speed as may be required, and the arrival at logical start and stop dates for the project activities(Goldratt, 1997). Inflation assists in identifying which sections requires the most effort in order to remain on schedule as well as to determine the likelihood that alternative plans will aid in meeting deadlines. It also helps to assess the consequences of alterations in the project. Since the PERT methodology is mainly applied when an activity estimates are probabilistic, we ends up creating contingency reserves as we try to derive the expected time. The contingency reserves help reduce the danger of losing huge resources that may occur should a project fail to meet the expected standards.
However, inflation has disadvantages. Disadvantages results from the simplistic assumptions made during the analysis of the project and its completion times. For example, there may be an assumption that once we have identified the critical path earlier in the process, it does not change. However, there is a high probability that the path chosen does not end up as the critical path. This is because it was selected based on the expected duration it will take to complete the project. With PERT, we ignore the scenarios where another path actually takes more time than the established critical path. There has been a noted tendency to underestimate the completion time and this leads to late completion. Furthermore, basing schedules on the raw work estimates alone is too risky (Filicetti et al, 2009). Complexities may arise as a result of increases number of activities and their dependencies. This is because, these extra activities had not been forethought, and no plans had been laid down for them. Another shortcoming is that PERT defines the initial, optimistic, and pessimistic estimates inadequately. This inadequacy makes the deadlines set to be impossible to meet if the project is to be of high standards. Alternatively, the organisation may be forced to hurry up in which case they miss important steps (Fleming, 2005). A common observation is that when time is under estimated, the quality of a project is compromised. To counter this, it may be necessary to re-negotiate the deadline with all stakeholders.
Like other techniques, PERT helps in breaking down activities into more details. Comparing PERT with CPM shows that the two gives the same results: critical activities and paths with zero slack time (Richard, 2000). However the two methods do not treat time the same way. While PERT takes time to be random, CPM methodology requires the time value to be deterministic in every activity. Another difference is that PERT’s focus is entirely on time whereas CPM is the analysis of the tradeoff between time and cost.
Lastly, the ability to incorporate uncertainty during the estimation of project times makes PERT superior compared to other methodologies (Filicetti et al, 2009). However, it may be important to remember that all the assumptions made during the PERT methodology do not necessarily result in accelerated progress of a project. Whenever project activities happen to increase, the increase requires more time and more funding, it may also be difficult to convince the management to allocate additional resources. The longer they take to see the need, the more is the time wasted, and this definitely leads to delays (Deming et al, 1989).
Such management decisions take time because resources such as time and money can never be in surplus. When greater quantities of resources are required than available, it would be reasonable for the management to compromise some less important tasks such that the organisation makes the best use of the available res ones. Any adjustments made affect the project duration and the timing of activities. This makes it very important that when we are using PERT, we should ensure that the assumptions are logical to avoid uncontrolled changes in later stages.