What characterizes a 'retrospective study'?

A retrospective study is characterized by its focus on examining past data to analyze outcomes. This type of study typically involves looking back at existing records, or previously collected data, to identify trends, outcomes, or relationships based on historical information. Researchers often use this approach to explore associations between exposures or interventions and outcomes that have already occurred.

In a retrospective study, data is gathered after the events have taken place, which distinguishes it from prospective studies that collect data moving forward from a defined starting point. This design is particularly useful in settings where it is impractical or unethical to conduct a prospective study, as it leverages already available data to draw conclusions.

The other options illustrate different characteristics that do not pertain to retrospective studies. For example, predicting future trends pertains to prospective studies, while collecting data through new interventions would align with experimental or prospective study designs. Lastly, focusing solely on current participants is characteristic of cross-sectional studies, which analyze data at a specific point in time rather than examining historical data.