Which of the following is an example of a practical investigation?

A practical investigation involves hands-on, empirical methods to gather data and draw conclusions based on real-world observations and experiments. Clinical trials of pharmaceuticals are firmly grounded in this definition as they include systematic procedures where new drugs are tested on participants in controlled environments to assess their safety and efficacy. These trials require the collection of data through direct interaction with subjects and the tangible evaluation of outcomes based on specific protocols.

In contrast, surveys on patient satisfaction primarily gather subjective responses from individuals without employing experimental methods. Theoretical analysis of healthcare delivery revolves around models or concepts that may not necessarily involve actual data collection in the field. Similarly, historical reviews of medical practices involve examining existing literature or records rather than conducting new empirical research. Thus, they do not fit the definition of practical investigations, which are characterized by active experimentation and data collection.