Simplified Program Evaluation and Review Technique (PERT)

A Review of Activity Time Distributions in Risk Analysis

“…Their method was not popular because of much computation time required for an approximate solution to be obtained even for small project networks. Cottrell [36] developed a simplified version of PERT using normally distributed activity times. The simplification was obtained by reducing the number of estimates required for activity durations from three, as in classical PERT, to two (the most likely-m, and the pessimistic-b times) which were subjectively chosen.…”

Analysis of the Influence of a Strategy-led Planning Approach on Successful Construction Project Implementation

“…Due to the unique nature of construction projects, historical data can become less meaningful or meaningless at worst, if the relevant context is unknown. Cottrell (1999) provides this criticism of the applicability of the PERT algorithm, that having three points estimates (pessimistic, optimistic and most-likely duration), is ambiguous for each and every activity. Advancements to the traditional planning algorithms in literature do not consider the requirement for generalspecific relationships and focus only on changing mathematical assumptions (for example: deriving equations by assuming alternative probability density functions) (Cottrell, 1999;Zhao, You and Zuo, 2010).…”

“…Cottrell (1999) provides this criticism of the applicability of the PERT algorithm, that having three points estimates (pessimistic, optimistic and most-likely duration), is ambiguous for each and every activity. Advancements to the traditional planning algorithms in literature do not consider the requirement for generalspecific relationships and focus only on changing mathematical assumptions (for example: deriving equations by assuming alternative probability density functions) (Cottrell, 1999;Zhao, You and Zuo, 2010). Therefore the findings of this study, along with the suggestions in literature, justify the limitations of the principles of classical statistics to cope with uncertainties in real-world scenarios.…”

“…However, many suggestions (Fallah Ashtiani and Aryanezhad, 2010;Lu and Lam, 2008) are still based on the extensive use of mathematics, preferably frequentist statistics, and hence subjected to similar inadequacies as of traditional planning algorithms (Dias, 2002). It is empirically found that actual data related to construction project planning does not satisfy axiomatic assumptions associated with statistical procedures (Cottrell, 1999).…”

Assessment of productivity and duration of highway construction activities subject to impact of rain

“…Because a number of uncertainties may be involved during construction, deterministic scheduling methods such as bar chart and critical path method (CPM) assuming a single fixed time of each project activity, usually are not adequate to correctly predict activity duration. Improvements to deterministic approaches include the use of probabilistic scheduling such as program evaluation review technique (Cottrell, 1999;Moder & Phillips, 1983), probabilistic network evaluation technique (Ang & Abdelnour, 1975), and Monte Carlo simulation technique (Crandall & Woolery, 1982;Lu & AbouRizk, 2000). However, these probabilistic techniques are incapable of assessing uncertainties, which are linguistic and subjective in nature.…”