Approaches to ensuring completeness in estimating

Poor estimates of project duration are rarely down to minor errors in mathematical formulae

The main problems are:

over-optimism, especially if estimators are involved in justifying the project costs
an expectation that estimates will be wrong, because we've always accepted it in the past
forgetting major activities

eg. installing software at many sites, data set up, user training

Question: How can we ensure that all activities have been included?

Two approaches to identifying tasks

Task-based approach

eg. Work Breakdown Structure
developed into Critical Path etc

Product-based approach

Product Breakdown Structure
Product Flow Diagram
Product Descriptions
Critical Path etc can be derived

Task-based approach

WBS

The Work Breakdown Structure is the traditional tool for devising lists of tasks

The WBS can be conceived as a tree, with the project as the root node, major components of the project as the main branches, and tasks/subtasks branch off from these. A WBS may be a diagram or a text list.

It is up to the project manager to ensure that all the tasks are included.

Question: What can we do to ensure the list is complete?

Example of a textual WBS

33.01 MOBILIZATION AND PREPARATORY WORK

33.01.01 MOBILIZATION OF CONSTRUCTION EQUIP. AND FACILITIES

33.01.02 MOBILIZATION OF PERSONNEL

33.01.03 PRECONSTRUCTION SUBMITTALS/IMPLEMENTATION PLANS

33.01.03.01 Erosion Control Plan

33.01.03.04 Environmental Protection Plan

(etc)

33.01.03.14 Construction Quality Control Plan

33.01.04 SETUP/CONSTRUCT TEMPORARY FACILITIES

(etc)

33.01.05 CONSTRUCT TEMPORARY UTILITIES

33.02 MONITORING, SAMPLING, TESTING, AND ANALYSIS

33.02.03 AIR MONITORING AND SAMPLING

(etc)

33.03 SITE WORK

33.03.04 ROADS/PARKING/CURBS/WALK

33.03.04.03 Aggregate Surfacing

(Source: US Army Corps of Engineers)