Final answer:
Free text describing a patient's complaint is unstructured data, which is not easily analyzed by conventional methods due to the lack of a specified format.
Step-by-step explanation:
Free text describing a patient's chief complaint is an example of unstructured data. Unstructured data is information that does not adhere to a specific format or structure, making it challenging to collect, process, and analyze through conventional databases and data models. In the context of healthcare, unstructured data can include physician's notes, patient interviews, and free text descriptions of symptoms, all of which can contain valuable insights into a patient's health but require more complex methods to extract usable information.