Expert Judgment and Project Activities

Project managers can use the special skills or knowledge of experts when activity duration estimating. This is known as the expert judgment process. It involves consulting with groups or individuals with specialized knowledge or training. These people can provide ideas and the probability of occurrence based on experience. There are four sources of expert judgment available to help you on your project.

• Other units or departments within the performing organization. Ideally, this is the best place to obtain expert judgment. It can be obtained at no cost to you. For example, if you need to know how long it takes to assemble an automobile, you can ask someone who works on the assembly line.

• Consultants. Consultants can be hired from outside the company to serve as experts for a project. However, this source is expensive and can cause costs to rise on a project. For example, a company that specializes in natural gas may be hired to consult on a pipeline project.

• Professional and technical associations. Professional and technical groups can provide expert judgment when the information needed is very detailed or technical. For example, if you need to know what the building code is for a residential home, you could ask the local builders association.

• Industry groups. Industry groups can offer general information. For example, if you need to know how long it takes for cement to cure, a construction group would be able to answer your question.

Once you've determine which expert or group of experts can help you during activity duration estimating, you can use three techniques to obtain the expert judgment you need.

• Interviews. Interviews can be on a one-to-one or a many-to-one basis. Interviews are conducted by asking a series of questions that will increase your knowledge of the project or a particular project activity.

• Brainstorming. Brainstorming works by getting a group to focus on a problem and then coming up with as many solutions as possible. Once the session has resulted in a number of solutions, the results can be analyzed.

• Historical data. Historical data uses the knowledge gained on a similar past project activity to obtain duration estimates for each activity associated with a current project.

While a certain technique might be appropriate in some situations, in others the same technique wouldn't give you the information you need. Interviews are best used when knowledgeable, experienced people are available at an affordable cost and specific information is needed, while brainstorming is best used when input from multiple experts is needed or when experienced people aren't available. Historical data is best used when records are accurate and both projects are similar.
There are many advantages to using the expert judgment technique for estimating activity duration. The advantages are that it:

• allows for different perspectives
• makes valuable use of prior knowledge and experience
• helps you find creative solutions
• helps you avoid re-inventing the wheel.

Expert judgment, like so many things, also has disadvantages. You have to be careful when using expert judgment, because it can be time consuming. It also can tie up experienced staff for many hours, to the detriment of other projects.
In addition, expert judgment can be costly if you have to go outside your company to hire experts. Another disadvantage is that experts may tend to downplay the fact that an activity took longer than expected on past projects.

Used wisely, though, expert judgment is a powerful and invaluable tool for estimating activity duration. It allows for different perspectives and more creative solutions. Most importantly, when you use expert judgment, your team will be less likely to re-invent the wheel.