Introduction In project management, every project is composed of stages or steps that must be followed before the project can be completed or finished. Estimation can be defined as the process of scheduling tasks and the budgeting of resources for those tasks. The two most important components of these steps or stages are scheduling and budgeting. However, the difficult aspects of project management remain those centred on estimating task duration, including the execution and monitoring of tasks (Burns and Janamanchi, 2007). Project scheduling is using known project tasks (activities) and putting them into a timeline while project budgeting refers to the allocation of funds to the proposed tasks and deciding how, when and where such funds will be utilized. Assumptions are made in both cases before accuracy of estimate is established. In a nutshell, estimation of tasks that make up a project refers to scheduling and budgeting. Methods use for Estimating Task Duration The concept of estimating task duration cannot be thoroughly understood without, firstly, knowing what comprises the work breakdown structure. The use of planning and monitoring of projects and its importance and significance in project management is largely based on the degree of accuracy exhibited during estimation of task duration. In the past, numerous professionals have used different technique to explain this concept ranging from probabilistic to real time (Illumoka, 1987). Hill et.al (2000) itemized expert judgement, parametric models, function point analysis and newer approaches such as neural networks and case based reasoning. Wysocki (2009) suggested six methods, which include; Delphi technique, Expert advice, Historical data, Similarity to other activities or analogous estimation, Threepoint technique and Wide-band Delphi technique.
Expert advice This method of estimating task duration involves the use of expertise opinion from either an individual or group of individuals with vast experience in that field of endeavour. In modern practice of project management, the most commonly used method for estimating task duration is the experts’ opinion, and the reason is, it does not require any previous or simply historical data of the subject upon which the estimate is carried out on. Results of numerous findings suggest it to be very accurate although objectivity of likely impediment, and their resulting analysis remained a challenge to address when using this method. In fact, many view it to be more of a subjective form of estimating task duration as against being objective, since the opinion of experts cannot be directly separated from their real experience (Goodman, 1992). In June, 2012, the sister organization to that which I work (Royal Group International) considered upgrading it corporate headquarter s’ office complex to a state-of-the-art facility, to further the yearnings of its business development strategy. I was saddled with the responsibility of sourcing for prospective vendors. The main component in the work was to change the front facade to fibre reinforced shattered proof glass in form of Aluminium curtain walls. My estimation of the task duration stood at four (4) weeks for completion. However, I at no time gave consideration for the sequential stages required to achieve the task; mobilization, fabrication, production, transportation and installation, simply because I was not an expert in such works and not at any time consulted any prior then. The period elapsed and additional period of four (4) elapsed without any tangible progress. After eight weeks without any tangible progress, I decided to consult an expert for advice, someone with thirty five (35) years experience in such works. My first meeting with him said it all after giving the project brief and specification. Within two working days, a new geometry for the works was suggested by the expert after his site visit, and has proposed to execute the work within ten (10) weeks from...
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