Question

In 500 words please tell me "What are three methods of duration estimation for project activities and what are the advantages and disadvantages of each method?" APA citation as reference used.

Answer 1

Three methods of duration estimation for project activities and advantages and disadvantages of each method:-

1.PERT Method

The Program Evaluation and Review Technique, or PERT, estimation method is a weighted average of three scenarios. First, compute the averages for optimistic, pessimistic and most likely time scenarios. PERT gives more weight to the most likely scenario, so multiply that average by four. Combine this result with the optimistic and pessimistic averages, and divide the result by six to come up with a final estimate. The optimistic scenario presumes all goes well, and you can complete the activity without issues. Conversely, with the pessimistic scenario, you imagine everything will go wrong and it’ll take longer to complete the activity. The most likely scenario assumes you can complete the activity without surprises. The PERT estimation method is a good option if you’re uncertain about the activities. It also enables you to consider all associated risks.

Advantage: Large Project Planning

• A PERT chart makes planning large projects easier, according to the University of Pittsburgh School of Information Sciences. It answers three key questions about each activity that help managers identify relationships between tasks and task dependencies. These questions involve how long it will take to complete an activity, and which other activities must occur immediately before and immediately after this activity for effective project completion. PERT is a good way of making these relationships visible in a diagram.

Advantage: Visible Critical Path

• The critical path includes all activities that cannot be delayed without affecting the project completion date. PERT makes the critical path visible, as explained by the University of Virginia. All tasks not on the critical path can have some slack time without affecting project completion time. When the project manager must delay one task to allocate more time to another, the critical path makes clear which tasks cannot be delayed.

Disadvantage: Complicated Charts

• PERT charts can be complicated and confusing, with hundreds or even thousands of tasks and dependency relationships, as noted by the University of Pittsburgh. This is especially true of very large projects. PERT diagrams can be expensive to develop, update and maintain.

Disadvantage: Prediction Inaccuracies

• PERT charts depend on the ability to predict precise time frames for multitudes of tasks. Complicated projects involving many activities and suppliers can make this prediction difficult, as explained by U.S. Legal Definitions. Unexpected events occur, and sometimes the original estimate of time needed for specific steps was inaccurate. PERT works best in projects where previous experience can be relied on to accurately make these predictions.

2.Analogous Estimation

The analogous, or top-down, estimation relies on information from similar projects to determine the activity duration for a current project. You’ll need historical data and a degree of expertise about the similar projects, because the reliability of your estimation depends on how closely the activities match the projects you're using as comparisons. Use this method at the beginning of a project when you don’t have all the details. Adjust the estimates as you learn more about the tasks and how long they can be expected to take with the resources available.Analogous estimation is done at initial stages of projects where management has to decide either to go for this project or not - or management is looking for a quick suggestion from a Project Manager.

Example of Analogous Estimation

We want to calculate how much concrete is required to build a house. For this, you need to have high-level historical data of a similar house.

Advantages of Analogous Estimation

• Most simple technique without any hectic calculations
• Works best if only a few details are available
• Quick and fast output
• Lest costly and not time-consuming

The disadvantage of Analogous Estimation

Accuracy is a question unless you have a history of the same project.

3.Bottom-up Estimation

Bottom-up estimation is one of the most traditional project estimation techniques. When you have a strong level of details for the project, you can create a complete assessment of tasks and resources you will need to complete the project.

This method involves using a work breakdown structure. You estimate each task one by one. You then roll up all your estimates to get the total project estimate. Depending on the project management software you use, you can automate a lot of this.

Advantages of the Bottom-Up Approach

This bottom-up approach calls for you to document all requirements. Then you can take a look at the big picture and the feasibility of your project management plan.This methodology is your most accurate approach to estimating because it deals with project components at a micro level, which makes them easier to wrap your head around. If you mix in a little top-down methodology and incorporate analogous and historic data, you can push accuracy even closer to reality. The unspoken perk of bottom-up estimates is the fact that they’re traceable; built from a list that covers your scope and all assumptions. As project details change (and they will) you can easily reference this list, make adjustments and see how changes impact time and cost.

Disadvantages of the Bottom-up Approach

While this is a very accurate method of estimation, it is the most time-consuming of all the project estimation techniques. It can take weeks to months to gather all the known requirements and document them in your budget planning tool or system.

Once that is complete, you need to compile the tasks. From there, you can see a final delivery date and budget.In some industries, such as the software industry, for example, this method has more severe drawbacks due to what’s called the speed of change. This refers to the rapid rate at which new development tools and new information becomes available.

Any project delay could mean that a competitor could make your current project obsolete before you have a chance to roll it out.