Final answer:
Humphrey's data collection method was an ethical breach as it involved deception, failing to respect participant privacy, and potentially affecting data reliability.
Step-by-step explanation:
Humphrey's collection of data for the tearoom trade study under the pretense of being a lookout is an example of a violation of the principle of ethical treatment of research participants. When conducting field research, especially involving human participants, researchers are expected to maintain fair and ethical treatment, which includes respect for privacy and the provision of anonymity when required. However, by misrepresenting his identity and intent, Humphrey breached these ethical considerations and, in doing so, influenced the natural behaviors of the participants, which could have led to unreliable data due to the Hawthorne effect. To ensure ethical standards are met, informed consent from participants is necessary, and researchers should avoid deceiving subjects about the nature of the study.