Final answer:
The distinction between primary and secondary data is determined by the purpose of the investigation: primary data is collected specifically for the current study, while secondary data is previously collected for other purposes. Option d is the correct choice.
Step-by-step explanation:
The distinction between primary and secondary data in research pertains to the origin and method by which the data was collected. Primary data refers to data gathered firsthand by the researcher through methods such as surveys, interviews, experiments, and direct observations. This kind of data is original to the investigation and is collected with the purpose of addressing specific research questions.
On the other hand, secondary data consists of information that has already been collected by others and is used by the researcher after-the-fact. Examples include books, articles, and previously conducted studies. Therefore, the answer to the question is d. purpose of the investigation, as primary data is collected specifically for the current research purpose, whereas secondary data has been previously collected for some other purpose.
In the context provided, the Middletown study by John S. Lynd and Helen Merrell Lynd mainly utilized primary research through fieldwork, which would involve surveying participants, as opposed to relying on secondary data. Fieldwork and surveys are examples of methodologies employed in primary research, as the investigator is directly involved in the data collection process.