What type of research design do investigators use for studying the same group of participants at many points in time?

A) cross-sectional
B) longitudinal
C) sequential
D) experimental

Longitudinal design involves studying the same group of participants over a period of time and collecting data at several points in time. This allows for the examination of changes or stability in the participants over time. Cross-sectional design, on the other hand, involves studying different groups of participants at one point in time. Sequential design is a combination of cross-sectional and longitudinal designs, where different groups of participants are studied longitudinally at different times. Experimental design is focused on manipulating independent variables to measure the effect on dependent variables and is not specific to the study of the same group of participants at multiple timepoints.