Bottom-up |
It establishes criteria for estimating the duration and costs at the lower levels of the WBS, to obtain a list of resources needed for the project, allowing the sum of all smaller packages to establish the cost and duration of the project. This estimation model is usually considered the most labor-intensive, but also the most accurate. |
PMI (2017)Project Management Institute – PMI. (2017). Um guia do conhecimento em gerenciamento de projetos (guia PMBOK) (6. ed.). Pennsylvania: Project Management Institute, Inc., Santos (2015)Santos, J. A. (2015). Gestão de Projetos. Curitiba: Universidade Positivo.
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Top-down or Analogy |
The total cost of the project is considered for later detailing the activities and feasibility of executing the project; |
Santos (2015)Santos, J. A. (2015). Gestão de Projetos. Curitiba: Universidade Positivo., Rad (2002)Rad, P. F. (2002). Project estimating and cost management. Vienna: Editora Management Concept. , PMI (2017)Project Management Institute – PMI. (2017). Um guia do conhecimento em gerenciamento de projetos (guia PMBOK) (6. ed.). Pennsylvania: Project Management Institute, Inc. , Rad (2002)Rad, P. F. (2002). Project estimating and cost management. Vienna: Editora Management Concept. , PMI (2017)Project Management Institute – PMI. (2017). Um guia do conhecimento em gerenciamento de projetos (guia PMBOK) (6. ed.). Pennsylvania: Project Management Institute, Inc.
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An analogous activity is the basis for duration estimation and costs estimation of one future activity; |
The purpose is to apply the estimation to situations of scarce information, allowing making assumptions about some environmental and functional characteristics of the project, even if its result is still imprecise; |
This model is more reliable when it uses previous projects that are really similar as a base, and require preparation and technical ability from the person responsible for the estimation. |
Parametric and Modular |
They are performed using the project characteristics in mathematical models and algorithms; |
Barcellos et al. (2003)Barcellos, M. P., Figueiredo, S. M., Rocha, A. R., & Travassos, G. (2003). Utilização de métodos paramétricos, analogias, julgamento de especialistas e conhecimento original no planejamento de tempo, custo de projetos de software. In Anais do II Simpósio Brasileiro de Qualidade de Software (pp. 1-15). São Paulo: SBC., PMI (2017)Project Management Institute – PMI. (2017). Um guia do conhecimento em gerenciamento de projetos (guia PMBOK) (6. ed.). Pennsylvania: Project Management Institute, Inc. , Santos (2015)Santos, J. A. (2015). Gestão de Projetos. Curitiba: Universidade Positivo. , Rad (2002)Rad, P. F. (2002). Project estimating and cost management. Vienna: Editora Management Concept. , PMI (2017)Project Management Institute – PMI. (2017). Um guia do conhecimento em gerenciamento de projetos (guia PMBOK) (6. ed.). Pennsylvania: Project Management Institute, Inc. , Rad (2002)Rad, P. F. (2002). Project estimating and cost management. Vienna: Editora Management Concept. , Barcellos et al. (2003)Barcellos, M. P., Figueiredo, S. M., Rocha, A. R., & Travassos, G. (2003). Utilização de métodos paramétricos, analogias, julgamento de especialistas e conhecimento original no planejamento de tempo, custo de projetos de software. In Anais do II Simpósio Brasileiro de Qualidade de Software (pp. 1-15). São Paulo: SBC. , PMI (2017)Project Management Institute – PMI. (2017). Um guia do conhecimento em gerenciamento de projetos (guia PMBOK) (6. ed.). Pennsylvania: Project Management Institute, Inc.
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Consider statistical relationships between historical data and variables (square meter, kilometer run, speed, etc.) necessary to calculate cost estimates for a work package; |
The results from these estimates are highly accurate and can be applied to an entire project or to parts of the project; |
These models are more appropriate in phases that have greater maturity of project objectives, and at more detailed levels of the WBS. |
Proportion |
It is one of the most basic forms of estimation in civil construction, in industrial and process projects. Its main premise is that there is a linear relationship between cost and duration of the project, as well as between one or more basic characteristics of the project. The basic features in this process are related to any physical or performance attribute. The quotients or factors are refined from personal experience, company archives or published scientific data. |
Rad (2002)Rad, P. F. (2002). Project estimating and cost management. Vienna: Editora Management Concept.
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Expert judgment |
Developed through consultations with specialists in various areas of activity, related to the project activities, in order to prepare the cost estimates of these activities. |
Rad (2002)Rad, P. F. (2002). Project estimating and cost management. Vienna: Editora Management Concept., Barcellos et al. (2003)Barcellos, M. P., Figueiredo, S. M., Rocha, A. R., & Travassos, G. (2003). Utilização de métodos paramétricos, analogias, julgamento de especialistas e conhecimento original no planejamento de tempo, custo de projetos de software. In Anais do II Simpósio Brasileiro de Qualidade de Software (pp. 1-15). São Paulo: SBC. , Carvalho & Rabechini (2011)Carvalho, M. M., & Rabechini, R. J. (2011). Fundamentos em gestão de projetos: construindo uma competência para gerenciar projetos. São Paulo: Editora Atlas.
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Interval Estimation |
It results from obtaining three possible estimates of duration of activities, most likely, optimistic and pessimistic. The most probable estimative is based on the most probable scenario in which the allocated resources are available and the other assumptions of the project are also observed. The optimist is based on the use of more positive duration estimates. The pessimist, conversely, considers the duration estimates to be more negative, and thus longer; |
Rad (2002)Rad, P. F. (2002). Project estimating and cost management. Vienna: Editora Management Concept., PMI (2017)Project Management Institute – PMI. (2017). Um guia do conhecimento em gerenciamento de projetos (guia PMBOK) (6. ed.). Pennsylvania: Project Management Institute, Inc. , Santos (2015)Santos, J. A. (2015). Gestão de Projetos. Curitiba: Universidade Positivo. , Carvalho & Rabechini (2011)Carvalho, M. M., & Rabechini, R. J. (2011). Fundamentos em gestão de projetos: construindo uma competência para gerenciar projetos. São Paulo: Editora Atlas.
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When a set of three estimates is obtained for all the elements of the WBS, a random number generation tool can be used, allowing evaluating the distributions and obtaining the most probable estimates based on the random selection of the estimates of each element. |