Variation, defined for this research as the time difference between what was planned and what actually happened, is important as it can impact the productivity performance of construction tasks. The construction process is complex and consists of a large number of interdependent tasks. When the starting time and/or duration of one task varies, it can affect other downstream tasks and result in disruptions to the schedule and/or decreased productivity. The research examined the impact of using a risk assessment matrix in conjunction with the Last Planner System® (LPS) to reduce and/or eliminate task duration variation. A mechanical contractor that specializes in plumbing, heating, ventilation, and air conditioning, compared the performance of two separate, but similar projects. The LPS® was used with one of the projects and the company's traditional planning system (i.e. the project didn't use the LPS®) was used with the other. Variation, productivity, and cost savings were analyzed using a risk assessment matrix and a benefit/cost ratio. The project that used the LPS® had a 35% higher productivity performance than the traditionally planned project and resulted in a benefit / cost ratio of 13:1. The research findings fill a gap in the body of knowledge by analyzing how planning can reduce variation with real project data. The results of this research illustrate the impact the LPS® can have on reducing variation and improving project productivity performance.