Monitoring process stability in quality improvement requires a tool that shows variation within acceptable limits over time.

Option A (Scattergram): Scattergrams show relationships between variables, not process variation.

Option B (Histogram): Histograms display data distribution, not variation over time.

Option C (Run chart): Run charts show trends but do not define expected variation ranges.

Option D (Control chart): This is the correct answer. The NAHQ CPHQ study guide states, “Control charts display process data over time with upper and lower control limits, indicating the expected range of variation in a stable process” (Domain 2).

CPHQ Objective Reference: Domain 2: Health Data Analytics, Objective 2.3, “Use data display tools,” emphasizes control charts for process stability. The NAHQ study guide notes, “Control charts monitor variation within defined limits” (Domain 2).

Rationale: Control charts assess process stability, aligning with CPHQ’s data analytics principles.