Why is the retention of a separate key for a coding system considered protective?

The retention of a separate key for a coding system is considered protective primarily because it safeguards sensitive information by controlling access to the data. When a separate key is used, only individuals who possess the key can link coded data back to identifiable participants. This separation creates a layer of security, reducing the risk of unauthorized individuals gaining access to personal identifiers tied to research subjects. By doing so, it helps maintain confidentiality and adhere to ethical research standards, especially when dealing with vulnerable populations, such as prisoners.

While options relating to simplicity, speed, and methodology may have their merits in data handling and analysis, they do not inherently provide the protective measure that a separate key confers in terms of data privacy and security.