A fundamental role of a project manager is simply answering the question, how long will specific tasks take to complete. While on the surface, the answer may seem simple, there are a couple of ways to answer this question.
When we look at the time it takes to complete a task, there are two different ways to answer the question. The question can either be answered in terms of duration or actual work.
To understand the difference, let’s define the two terms:
- Duration: is the total amount of time it will take to complete the task. When thinking about duration, think of how long the task will take in the traditional sense. For example, when most stakeholders ask when the task will be finished, they are asking about duration, as in we will finish on the 15th of April.
- Actual work (actual): this is the total amount of effort a task will take. A good example to understand this concept is a person painting a house. Let’s say this person is only available to paint for eight hours each day on Saturdays and Sundays because they work during the week. They expect to have the entire house painted in two weeks (duration). If we look at the actual work, we can say that the task will take 32 hours (four eight hour periods).
So in our example above, if asked how long it is going to take to paint the house, we could answer the question in two, both correct ways. If we answer with the duration, we would say two weeks but we could be equally correct in saying 32 hours.
This is a key concept in accurately planning projects. Usually, there are other projects or commitments that resources have that may not allow them to devote 100% of their available time to a specific project. Keeping in mind the difference between duration and actual work is critical to achieving and accurate picture of the true length of each task and the project as a whole.
Dan Thompson, PEI