The correct answer is D, "Study," as this is the step in the Shewhart/Deming cycle (commonly known as the Plan-Do-Study-Act [PDSA] cycle) where the results of the interventions are compared with the original goal. According to the Certification Board of Infection Control and Epidemiology (CBIC) guidelines, the PDSA cycle is a systematic approach to quality improvement, widely used in infection control programs to test and refine interventions. The cycle consists of four stages: Plan (designing the intervention and setting goals), Do (implementing the intervention on a small scale), Study (analyzing the data and comparing outcomes against the original goal), and Act (standardizing successful changes or adjusting based on findings) (CBIC Practice Analysis, 2022,Domain IV: Education and Research, Competency 4.2 - Evaluate the effectiveness of educational programs). The Study phase is critical for assessing whether the intervention achieved the intended reduction in infection rates or other performance metrics, providing evidence to guide the next steps.

Option A (Do) involves the execution of the planned intervention, focusing on implementation rather than evaluation, so it does not include comparing results. Option B (Act) is the final step where successful interventions are implemented on a broader scale or adjustments are made, but it follows the comparison made in the Study phase. Option C (Plan) is the initial stage of setting objectives and designing the intervention, which occurs before any results are available for comparison.

The emphasis on the Study phase aligns with CBIC’s focus on using data to evaluate the effectiveness of infection prevention strategies, ensuring that performance improvement projects are evidence-based and goal-oriented (CBIC Practice Analysis, 2022, Domain II: Surveillance and Epidemiologic Investigation, Competency 2.4 - Evaluate the effectiveness of infection prevention and control interventions). This step enables the infection preventionist to determine if the original goal—such as reducing healthcare-associated infections—was met, facilitating continuous improvement.