Which of the following is often used to measure the impact of a process improvement project on business results?

The option indicating ROI, or Return on Investment, is the most appropriate choice for measuring the impact of a process improvement project on business results. ROI provides a quantitative assessment of the financial benefits of a project relative to its costs. It allows organizations to evaluate how effectively their investments in process improvements translate into gains, such as increased revenue, reduced costs, or improved efficiency.

In the context of process improvement, calculating ROI helps stakeholders understand the value generated from the implementation of new processes or systems. This financial metric can inform decision-making and justify further investments in improvement initiatives.

On the other hand, the other methods mentioned serve different purposes. For instance, DOE (Design of Experiments) focuses on experimental design and optimizing processes rather than measuring outcomes directly. CTQ (Critical to Quality) pertains to defining quality metrics that matter to customers, which doesn't directly quantify business results. FMEA (Failure Mode and Effects Analysis) is a proactive tool for risk assessment designed to identify potential failures in a process but does not measure the overall financial impact of improvements. In sum, ROI is central to assessing the tangible benefits of process improvement against their costs, thus confirming its appropriateness for the question asked.