If a researcher asks any student walking out of the health center about their illness, what type of sampling is being used?

The correct answer is convenience sampling. This method involves selecting participants based on their easy availability and proximity to the researcher rather than through random selection or a predefined criterion. In this case, the researcher is approaching students who are already exiting the health center, making these individuals readily accessible for data collection.

This technique is commonly used in situations where it is not feasible to conduct a more rigorous sampling approach, such as random sampling, which would require a systematic method to ensure every individual has an equal chance of being included. Convenience sampling is often criticized for potentially introducing bias since the sample may not adequately represent the entire population. However, it is frequently employed in exploratory research and situations where quick data collection is necessary.