8-estimate activity duration, resource requirements, and cost

Dr Zain Yusufzai Chapter # 8 (Page #)

Estimate Activity Duration, Resource Requirements, and Cost

The duration of a project is the elapsed time in business working days, not including weekends, holidays, or other non working days. Duration is different from work effort. Work effort is labor required to complete an activity.

Causes Of Variation In Activity DurationThere are several causes of variation in the actual activity duration, as discussed in the following:

1. Varying Skill Levels2. Unexpected Events3. Efficiency of wok time4. Mistakes and Misunderstandings

Elapsed Time vs. Labor Time vs. Productive Time

It is also important to understand the difference between labor time and clock time.

If a person could work at perfect efficiency, he or she could accomplish ten hours of work in ten hours. Such a person would be truly unique, for what is more likely is daydreaming, learning time, a change of approach, rework and so on. Several estimates for how efficient a person is have been put forward. They typically range from 66 to 75 percent.

Resource Loading Versus Activity Duration

The duration of an activity is influenced by the amount of resources scheduled to work on it.

There is not necessarily a direct linear relationship between the amount of resource assigned to an activity and its duration.

Adding more resources to hold activity duration within the planning limits can be effective.

Doubling the resources sounds like a technology breakthrough in shortening duration.

New kinds of work will emerge from the addition of a resource to an activity

Another consideration for the project manager is the impact on risk that results form adding another resource

The more people working on an activity, the more likely one will be absent, the higher the likelihood of a mistake being made, and the more likely they will get in each other’s way

Variation in Activity Duration

Effective Project ManagementRobert K. Wysocki, Robert Beck Jr, David B. Crane

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Varying skill levels Unexpected events Efficiency of work time Mistake and misunderstandings

Six Methods for Estimating Activity Duration

Similarity to other activities Historical data Expert advice Delphi technique Three point technique Wide band Delphi technique

Five Methods for Estimating Activity Duration

1. Similarity to other activities Some of the activates in your WBS may be similar to activities completed in other projects

2. Historical Data This is getting ahead of ourselves somewhat but every good management methodology will contain a project notebook. In this note book you will have recorded the estimated and actual durations of activities. It is this historical record that can now be used on the current project.

3. Expert Advice When the project involves a breakthrough technology. In these cases you will have to appeal to outside authorities. Vendors may be a good source, as will non-competitors who are using that technology.

4. Delphi Technique This is a group technique that extracts and summarizes the knowledge of the group to arrive at an estimate.

5. Three-point Technique

In order to use the method we will need three estimates of activity duration: optimistic, pessimistic and mist likely. The optimistic time is defined as the shortest duration one has had or might expect to experience given that everything happens as was expected. The pessimistic time is that duration that would be experienced (or has been experienced) if everything that could go wrong did go wrong and yet the activity was completed. Finally the mist likely time is that time usually experienced.


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Estimation precision

Resources People Facilities Money Materials

People as a Resource

Skill Matrices Skill categories Skill levels

Estimating Duration as A Function Of Resource Availability

The Duration Itself The total amount of work, as in person hours/days that will

be done on the activity by a resource The percent per day of his or her time that the resource

can devote to working on it Assign as a total work and constant percent/day Assign as a duration and total work effort Assign as a duration and percent /day Assign as a profile

Estimating Cost

Material Costs Labor Costs

(JPP) session Get it roughly right Spend more effort on front end activities than on back end

activities Consensus is all that is needed


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8-estimate activity duration, resource requirements, and cost

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