Comparison of Project Scheduling techniques: PERT versus Monte Carlo simulation (original) (raw)
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International Journal of Integrated Engineering, 2020
One of the problems faced by the contractors is an inappropriate scheduling method. For project scheduling, the contractor using Bar chart. Although this method still can be used, but in its application is limited to scheduling large-scale projects, because this method cannot describe the interdependence of activity. The problem can be solved using Program Evaluation and Review Technique (PERT) and Critical Path Method (CPM). PERT is a method that can be used to estimate the duration of activity and can calculate the probability of project time completion, while CPM is a scheduling method used to find the path of critical path and can describe the relationship between activities. Scheduling results using CPM found that the minimum duration to complete the project was 135 days with 20 activities on the critical path with 50% project probability. Further analysis using PERT found that for a greater probability of the project completion was 68% for 139.78 days duration, 95% for 144.56 days, and 99.7% for 149.34 days.
2016 Portland International Conference on Management of Engineering and Technology (PICMET), 2016
Project managers are often confronted with the question on what is the probability of finishing a project within budget or finishing a project on time. One method or tool that is useful in answering these questions at various stages of a project is to develop a Monte Carlo simulation for the cost or duration of the project and to update and repeat the simulations with actual data as the project progresses. The PERT method became popular in the 1950's to express the uncertainty in the duration of activities. Many other distributions are available for use in cost or schedule simulations. This paper discusses the results of a project to investigate the output of schedule simulations when different distributions, e.g. triangular, normal, lognormal or betaPert, are used to express the uncertainty in activity durations. Two examples were used to compare the output distributions, i.e. a network with 10 activities in sequence and a network where some of the activities are performed in parallel. The results indicate that there is no significant difference in the output distributions when different input distributions with the same mean and variance values are used.
PROJECT MANAGEMENT WITH SIMULATION A critical view on the critical path
2000
A process-oriented simulation approach to project management is proposed which gives realistic statistical information about total project data and about individual activities as a function of contractual completion-time. The proposed method provides the possibility to define a generic activity network, which is simulated. The activities in the network may have any statistical or tabulated completion-time distribution. A project simulation run consists of a large number of sub-runs each simulating a project realisation. A run provides statistical information with respect to project completion-times, individual activities such as the probability of activities being critical and excess probability of contract time, and information for monitoring contract critical activities during project realisation. A case of aircraft maintenance is elaborated in which the model is used to reduce the number of contract time excesses using a simple rule assigning extra capacity to activities. The rul...
A deeper insight in some effects in project risk management
2014
This document shows a possible way how to deal with insecurities in the time schedule of a project plan. It shows that Program Evaluation and Review Technique (PERT), the most popular approach to handle this, bears some severe disadvantages. Furthermore it offers an alternative to overcome them by using Monte Carlo simulation. Finally it can be claimed that a complete change of paradigm is necessary: If you have any insecurities as inputs, everything becomes insecure. This might on the first sight convey the impression that the whole situation converts more complex, but we should rather accept this as the opportunity to apply all the well-known instruments from statistics.
This study presents the effectiveness of scheduling techniques in the success of mechanical construction projects as an essential tool for project planning, implementation, evaluation and control. Improper project resources scheduling leads to time and cost overruns, hence leads to a huge variation. This work focused on scheduled and unscheduled sets of constructed silo tanks. The analyses were based on the combination of scheduling techniques (CPM & Gantt chart) with the aid of Microsoft Project for the scheduled project sets, as these techniques helped in evolving a planned activity resource cost. The corresponding results of the implemented scheduled projects were related to cost per day and their performance evaluated based on earned value analysis. The scheduled and unscheduled project set results were analyzed based on the test of the null hypothesis using F-Test for the equality of variance. Research findings shows that, the combination of scheduling techniques were effective in reducing variance within the scheduled project set, while the earned value analysis exposed the minor variance which existed, the variance were not sufficient to deter the project success. The F-test upturned the null hypothesis and upheld the alternative hypothesis which stated that variance in unscheduled project were greater than those in scheduled project.
International Journal of Industrial and Operations Research, 2020
The project evaluation and review technique (PERT) and critical path method (CPM) were applied in a building construction company. Different activities involved in the house construction project were described. The earliest events, latest commencement and completion of activities were determined using Forward and Backward pass computations in CPM. Critical paths were determined using both CPM and PERT. Based on the analysis, it was shown that the completion of the house project using CPM was almost the same with that of PERT such that the difference between both techniques was only one day. The probability that the house construction project could be completed in 151 days was 99.87%. This implies that the house construction project could be completed on time using both techniques. However, the results showed that the implementation of both CPM and PERT methods are effective and efficient in a house construction project.
Probabilistic Completion Time in Project Scheduling
— There are two common used methods to find the minimum completion time for a project scheduling. These methods are Critical Path Method (CPM) and Program Evaluation Review Technique (PERT). In CPM, a network diagram, which is Activity on Node (AON), is drawn and the slack time for every activity is calculated such that the project's critical path could be found. It is important that the critical path can suggest the shortest possible completion time. On the other hand, PERT concerns on uncertainty and risk in a project. It has three time estimates, which are optimistic, pessimistic and most likely, and all the time estimates mentioned follows the beta distribution. Besides, the probability in completing the project within certain duration is calculated by using the standard normal distribution. As the risk cannot be avoided in a project, it is important to keep track on any changes and to minimize the completion time for a project. Both of the methods are used to calculate the shortest possible completion time, slack and critical path. The difference between these methods is CPM has only one determined time estimate, while PERT has three time estimates, which shows the uncertainty in the duration of an activity in a project. For illustration, the data used for the construction of a three-room house was studied. The results show that the minimum completion time for the project is 44 days with a success probability 0.91. In conclusion, CPM and PERT are practical tool in the project scheduling.
Schedule Risk Analysis Using Monte Carlo Simulation for Residential Projects
2019
Scheduling is an essential part of construction project management. Planning and scheduling of construction tasks help engineers to complete the project on time and within the budget. Most of the construction project failed to finish within planned duration; one of the reasons is regarded to estimated project duration without considering uncertainties that may cause a delay in performing specific activities. Hence it is vital to develop a risk management process which deals with the risks of execution that affects the project duration. This study focused on Schedule Risk Analysis Using Monte Carlo Simulation for Residential Projects, by taking the construction of a residential house as a case study. The primary objective of this study analyzes the output of a project schedule risk simulation when Monte Carlo use to simulate the duration of individual activities of the project and compare the total project duration outputs graphically and through statistical analysis. Consequently, using the Critical Path Method (CPM) to determine the project duration, which is equal to 96 days. For deciding the activity duration, the researcher has made a form. The form consists of all house tasks and estimated quantity with three columns for estimating Optimistic Duration, Most Likely Duration, and Pessimistic Duration in accordance with the respondent's perception for establishing the project duration by using the Program Evaluation and Review Techniques (PERT) method, which is equal 103 days. Project duration with low risk equal to 103 days, with base risks equal to 107 days and with high-risk project duration equal to 111 days. The outcomes clearly show that it is extremely unlikely to complete the project within 98 days and there is 100% chance that the project will be completed in 115 days. The sensitivity analysis for residential construction house indicates that the project schedule is most sensitive to the activity of "Wall Ceramic Tiles", which can influence the completion date because of the correlation coefficient of this activity reached to 0.39 and top-ranked of all other activities.
KSCE Journal of Civil Engineering, 2019
The Program Evaluation and Review Technique (PERT) model uses parameters such as the specified project completion time, mean, and variance to estimate the probability of project completion time. However, this model uses a weighted average and unweighted value in the variance, which is based on six sigma of the mean. Despite many proposed modifications to improve the traditional PERT model, the hidden error in the calculation of the variance and mean of the PERT approach has not been adequately addressed. This error leads to underestimation of the schedule risk. Considering the impact of variance and mean on the probability of project completion times, this study contributes to the improvement of the accuracy of schedule risk estimation by proposing a modified variance and mean of the original PERT model. The original PERT model was first used to estimate the project completion time. However, using the proposed modified model to estimate the completion time, a 95% confidence interval assumption and the corresponding distribution within ±2 standard deviation of the mean and standard or Z values were employed to model the new mean and variance equations. To prove the validity of the proposed modified variance and mean assumptions, we performed a schedule risk analysis through simulation using Oracle Crystal Ball for comparison. The results showed that the proposed PERT model had a better mean error rate of 2.46% as compared to 3.31% of the original PERT model.
NEW PERT and CPM in Project Management with Practical Examples
American Journal of Operations Research, 2021
This paper reviewed the concepts of Project Evaluation Review Technique and Critical Path Method in project management with practical examples. The methods and success of quantitative decision-making approaches in project management through the use of project evaluation review technique and the critical path method as regards project duration and critical activities of a project, were discussed. The review found that while both methods are effective in achieving success in project management, the relationship and connectivity of activities involved in a project life cycle are key aspects. The paper concludes that the project evaluation review technique is more effective when the duration of the project is uncertain, while the critical path method is effective when the project's end time is certain. The paper, therefore, recommends that to achieve maximum operative efficiency in utilizing resources in project management, prior to commencing the execution of a project, all required resources to cover every activity must be assembled and prioritized to eliminate interruptions that could bring delay and unnecessary cost implications. Again, policies focused on improving project execution should be implemented in developing nations to minimize the many cases of failed and delayed projects. Subsequently, stakeholders in projects must be given the right, under the law, to prosecute the government, its agencies and/or the executors of projects for failure to execute a project on schedule.