The project manager should use a Pareto chart to prioritize which defects to address for the product. A Pareto chart is a type of bar chart that shows the frequency or impact of different causes of problems or defects. It also shows a cumulative line that represents the percentage of the total frequency or impact. A Pareto chart can help to prioritize the causes that have the most significant effect on the quality of the product and apply the 80/20 rule, which states that 80% of the problems are caused by 20% of the causes.