Which type of study involves collecting data at a single point in time across multiple populations?

A cross-sectional study is designed to collect data at one specific point in time, allowing researchers to analyze and compare various populations or groups simultaneously. This type of study captures a snapshot of the observations, which can be valuable for identifying trends or disparities among different demographic or geographic segments.

In contrast, a longitudinal study involves repeated observations of the same subjects over an extended period, which allows researchers to track changes over time but does not provide the immediate comparison across different groups. A retrospective study looks back at data collected in the past, often involving historical data analysis, which does not meet the criteria of data collected at a single point in time. An experimental study typically involves manipulation of variables and observation of outcomes, which also distinguishes it from cross-sectional studies that simply observe and report based on existing conditions without intervention.