Which type of research utilizes data already collected by other researchers?

The correct answer is available data research, which specifically involves the use of data that has already been collected and compiled by other researchers for various purposes. This approach allows researchers to conduct new analyses without having to perform the original data collection themselves. It can be advantageous as it saves time and resources while also potentially providing access to a broader range of datasets than an individual researcher might be able to gather.

In contrast, case study research typically focuses on an in-depth examination of a single subject, group, or event, often involving firsthand data collection. Content analysis involves the systematic examination of communication artifacts, such as texts, media, or documents, and may also require the researcher to gather new data rather than relying on previously collected information. Primary data collection refers to the process of gathering original data directly from the source through methods such as surveys or experiments, which is distinct from utilizing existing data.