Discussion post Project Management - buffer

Scheduling is an inexact process in that it tries to predict the future. While it is not possible to know with certainty how long a project will take, there are techniques that can increase your likelihood of being close. If you are close in your planning and estimating, you can manage the project to achieve the schedule by accelerating some efforts or modifying approaches to meet required deadlines.

One key ingredient in the scheduling process is experience the project area; another is experience with scheduling in general. In every industry area there will be a body of knowledge that associates the accomplishment of known work efforts with time duration. In some industries, there are books recording industry standards for use by cost and schedule estimators. Interviewing those who have had experience with similar projects is the best way to determine how long things will really take.

When preparing a schedule estimate, consider that transition between activities often takes time. Organizations or resources outside your direct control may not share your sense of schedule urgency, and their work may take longer to complete. Beware of all external dependency relationships. Uncertain resources of talent, equipment, or data will likely result in extending the project schedule.

Things to consider when creating a schedule and/or managing time:

· Activity definition: Identifying the specific activities that the project team members and stakeholders must perform to produce the project deliverables.

· Activity sequencing: Identifying and documenting the relationships between project activities.

· Activity resource estimating: Estimating how many resources a project team should use to perform project activities.

· Activity duration estimating: Estimating the number of work periods that are needed to complete individual activities.

· Schedule development: Analyzing activity sequences, activity resource estimates, and activity duration estimates to create the project schedule.

· Schedule control: Controlling and managing changes to the project schedule.

Activity Duration Estimating and Schedule Development

Before estimating activity durations, you must have a good idea of the quantity and type of resources that will be assigned to each activity. Consider important issues in estimating resources:

· How difficult will it be to complete specific activities on this project?

· What is the organization's history in doing similar activities?

· Are the required resources available?

Duration includes the actual amount of time worked on an activity plus the elapsed time. Effort is the number of workdays or work hours required to complete a task. Effort does not normally equal duration. People doing the work should help create estimates, and an expert should review them.

--------------------------------------------------------------------------------------------------

The critical path is the series of events needed in order to complete the project successfully. The slack or float of the schedule is identified via this process. The slack (or float) is the amount of time an activity can be delayed without delaying the project. Sometimes this is calculated into the schedule as a buffer. For instance, if a task takes 2 days to complete, then we may allocate 3 days to the task. Another way is to allocate 2 days, but know that it could take 3 days.

Let's take the following tasks and create a diagram to represent the schedule or timeline of events for the project:

Web Design Project (of course, there will be much more to than this, but let's pretend this is it).

Activity	Task	Predecessors
A	Initial Meetings about Website	None
B	Purchase www. address	A
C	Determine the site map	D
D	Determine Content topics	A
E	Determine Ad placement	F
F	Create Layout of page	C
G	Create Navigation Buttons	C
H	Create Content	D
I	Create each page	H, F
J	Link each page	I
K	Finalize Website	B, J

From the tasks above along with their predecessors, we could create something like this:



We can see that some tasks can be completed simultaneously while others depend on one or two major tasks to be completed. Beyond this, we can allocate time and resources to each of the tasks.

Critical Path

The Critical Path is the sequential schedule of activities that determines the duration of the project. This type of analysis illustrates the schedule in diagram of networks connecting each task to each other and allowing for the visualization of the scheduled time of the project. This series of activities removes the linear portion of the project planning into a web of activities where some are done simultaneously.

The critical path does not necessarily contain all the critical activities; it only accounts for time. It contains all of the activities necessary with the shortest (earliest) time by which to complete them thus becoming critical to stay on track.