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Designed to help those that are preparing to take the PMP or CAPM Certification Exam, each post within this series presents a comparison of common concepts that appear on the PMP and CAPM exams.
Lead vs Lag
Lead and lag are two terms associated with the relationships that may occur between multiple schedule activities.
Lead is the acceleration of a successor activity. In other words, the second activity can begin (and be conducted in parallel) as the first activity.
Lead is only found activities with finish-to-start relationships: A must finish before B can start.
In order to leverage a lead, which will compress the total combined duration of both activities, the dependency must be discretionary, meaning that there is no physical limitation on completing A before B begins.
Lag is the delay of a successor activity and represents time that must pass before the second activity can begin. There are no resources associated with a lag.
Lag may be found in activities with all relationship types: finish-to-start, start-to-start, finish-to-finish, and start-to-finish.
The photo shoot will take four days and the photo editing will take six days. Instead of waiting until the end of the 4-day photo shoot to begin editing the pictures, we start editing after the first day of shooting. This brings the total duration from ten days down to seven days by leveraging the lead.
The photo proofs are sent to the customer upon completion of the shoot, however, there is a 15-day lag associated with the customer review before the printing of the photos can begin.
Lead and lag are both used in the development of the project schedule.
Lead is an acceleration of the successor activity and can be used only on finish-to-start activity relationships.
Lag is a delay in the successor activity and can be found on all activity relationship types.
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