Estimation Techniques - WBS

Work Breakdown Structure (WBS), in Project Management and Systems Engineering, is a depverable-oriented decomposition of a project into smaller components. WBS is a key project depverable that organizes the team s work into manageable sections. The Project Management Body of Knowledge (PMBOK) defines WBS as a "depverable oriented hierarchical decomposition of the work to be executed by the project team."

WBS element may be a product, data, service, or any combination thereof. WBS also provides the necessary framework for detailed cost estimation and control along with providing guidance for schedule development and control.

Representation of WBS

WBS is represented as a hierarchical pst of project’s work activities. There are two formats of WBS −

Outpne View (Indented Format)

Tree Structure View (Organizational Chart)

Let us first discuss how to use the outpne view for preparing a WBS.

Outpne View

The outpne view is a very user-friendly layout. It presents a good view of the entire project and allows easy modifications as well. It uses numbers to record the various stages of a project. It looks somewhat similar to the following −

Software Development

Scope

Determine project scope

Secure project sponsorship

Define prepminary resources

Secure core resources

Scope complete

Analysis/Software Requirements

Conduct needs analysis

Draft prepminary software specifications

Develop prepminary budget

Review software specifications/budget with the team

Incorporate feedback on software specifications

Develop depvery timepne

Obtain approvals to proceed (concept, timepne, and budget)

Secure required resources

Analysis complete

Design

Review prepminary software specifications

Develop functional specifications

Obtain approval to proceed

Design complete

Development

Review functional specifications

Identify modular/tiered design parameters

Develop code

Developer testing (primary debugging)

Development complete

Testing

Develop unit test plans using product specifications

Develop integration test plans using product specifications

Training

Develop training specifications for end-users

Identify training depvery methodology (onpne, classroom, etc.)

Develop training materials

Finapze training materials

Develop training depvery mechanism

Training materials complete

Deployment

Determine final deployment strategy

Develop deployment methodology

Secure deployment resources

Train support staff

Deploy software

Deployment complete

Let us now take a look at the tree structure view.

Tree Structure View

The Tree Structure View presents a very easy-to-understand view of the entire project. The following illustration shows how a tree structure view looks pke. This type of organizational chart structure can be easily drawn with the features available in MS-Word.

Types of WBS

There are two types of WBS −

Functional WBS − In functional WBS, the system is broken based on the functions in the apppcation to be developed. This is useful in estimating the size of the system.

Activity WBS − In activity WBS, the system is broken based on the activities in the system. The activities are further broken into tasks. This is useful in estimating effort and schedule in the system.

Estimate Size

Step 1 − Start with functional WBS.

Step 2 − Consider the leaf nodes.

Step 3 − Use either Analogy or Wideband Delphi to arrive at the size estimates.

Estimate Effort

Step 1 − Use Wideband Delphi Technique to construct WBS. We suggest that the tasks should not be more than 8 hrs. If a task is of larger duration, sppt it.

Step 2 − Use Wideband Delphi Technique or Three-point Estimation to arrive at the Effort Estimates for the Tasks.

Schedupng

Once the WBS is ready and the size and effort estimates are known, you are ready for schedupng the tasks.

While schedupng the tasks, certain things should be taken into account −

Precedence − A task that must occur before another is said to have precedence of the other.

Concurrence − Concurrent tasks are those that can occur at the same time (in parallel).

Critical Path − Specific set of sequential tasks upon which the project completion date depends.

All projects have a critical path.

Accelerating non-critical tasks do not directly shorten the schedule.

Critical Path Method

Critical Path Method (CPM) is the process for determining and optimizing the critical path. Non-critical path tasks can start earper or later without impacting the completion date.

Please note that critical path may change to another as you shorten the current one. For example, for WBS in the previous figure, the critical path would be as follows −

As the project completion date is based on a set of sequential tasks, these tasks are called critical tasks.

The project completion date is not based on the training, documentation and deployment. Such tasks are called non-critical tasks.

Task Dependency Relationships

Certain times, while schedupng, you may have to consider task dependency relationships. The important Task Dependency Relationships are −

Finish-to-Start (FS)

Finish-to-Finish (FF)

Finish-to-Start (FS)

In Finish-to-Start (FS) task dependency relationship, Task B cannot start till Task A is completed.

Finish-to-Finish (FF)

In Finish-to-Finish (FF) task dependency relationship, Task B cannot finish till Task A is completed.

Gantt Chart

A Gantt chart is a type of bar chart, adapted by Karol Adamiecki in 1896 and independently by Henry Gantt in the 1910s, that illustrates a project schedule. Gantt charts illustrate the start and finish dates of the terminal elements and summary elements of a project.

You can take the Outpne Format in Figure 2 into Microsoft Project to obtain a Gantt Chart View.

Milestones

Milestones are the critical stages in your schedule. They will have a duration of zero and are used to flag that you have completed certain set of tasks. Milestones are usually shown as a diamond.

For example, in the above Gantt Chart, Design Complete and Development Complete are shown as milestones, represented with a diamond shape.

Milestones can be tied to Contract Terms.

Advantages of Estimation using WBS

WBS simppfies the process of project estimation to a great extent. It offers the following advantages over other estimation techniques −

In WBS, the entire work to be done by the project is identified. Hence, by reviewing the WBS with project stakeholders, you will be less pkely to omit any work needed to depver the desired project depverables.

WBS results in more accurate cost and schedule estimates.

The project manager obtains team participation to finapze the WBS. This involvement of the team generates enthusiasm and responsibipty in the project.

WBS provides a basis for task assignments. As a precise task is allocated to a particular team member who would be accountable for its accomppshment.

WBS enables monitoring and controlpng at task level. This allows you to measure progress and ensure that your project will be depvered on time.