cross-sectional design
a research design in which individuals, typically of different ages or developmental levels, are compared at a single point in time. An example is a study that involves a direct comparison of 5-year-olds with 8-year-olds. Given its snapshot nature, however, it is difficult to determine causal relationships using a cross-sectional design. Moreover, a cross-sectional study is not suitable for measuring changes over time, for which a longitudinal design is required. See also cross-sectional analysis.