A medical researcher is studying the effectiveness of a new pain medication. To recruit participants, the researcher posts flyers in the waiting rooms of several local hospitals, inviting individuals experiencing chronic pain to volunteer for the study. 300 volunteers are enrolled, and the study finds that 85% report significant pain relief. Which of the following is the most accurate statement about the researcher's study design?
The study's findings can be generalized to all individuals experiencing chronic pain.
The sample is biased because it consists of volunteers who are already seeking medical care, potentially differing from the general population with chronic pain.
The sample size is too small to draw any meaningful conclusions about the medication's effectiveness.
The study design is robust because it targets individuals who genuinely need pain relief.
