What is the primary characteristic of cross-sectional research design?

The primary characteristic of cross-sectional research design is that all data is collected at a single point in time. This design allows researchers to analyze a specific population or phenomenon at a given moment, making it useful for assessing variables and their relationships without the time commitment that longitudinal studies require. By capturing a "snapshot," researchers can identify trends, patterns, and correlations among variables simultaneously, which can inform further studies or immediate application in various fields.

Other options touch upon different methodologies: collecting data over multiple time periods aligns more with longitudinal studies, which track changes over time. Collecting data from different samples in multiple populations relates to comparative or diverse sampling methodologies, while the notion of data collection occurring only once a year suggests a periodic approach more fitting for longitudinal analysis rather than the stationary nature of cross-sectional designs.