A Quality-Adjusted Life Year (QALY) is a measure used to evaluate the value of medical interventions. It combines both the quantity and quality of life gained from a treatment. One QALY equates to one year of life in perfect health. If a treatment allows a person to live for one additional year but with a quality of life rated at 0.5, it would count as 0.5 QALYs. QALYs are often used in health economics to compare the effectiveness of different treatments or interventions. This helps policymakers and healthcare providers allocate resources efficiently, ensuring that the most beneficial treatments are prioritized for patients.