Outline the three types of longitudinal research designs. What are the strengths and potential weaknesses of each?

What will be an ideal response?

Repeated cross-sectional design (trend study)--a type of longitudinal design in which data are collected at two or more points in time from different samples of the same population; Trend studies allow researchers to describe long-term changes in the population. Trend studies are also flexible and can be inexpensive especially when a researcher uses secondary data analysis; trend studies present problems with internal validity since it can only be used to describe a certain period of time; fixed-sample panel design (panel design)--a type of longitudinal study in which data are collected from the same individuals--the panel--at two or more points in time. Some panel designs allow researchers to replace panel members who leave with new ones; panel designs are helpful to use when looking at the dynamics of change such as looking at the roles of the media in changing political views as well as used to predict long-term effects; panel designs can be expensive as well as having high attrition rates (often losing more than a quarter of their subjects) and subject fatigue; event-based design (cohort study)--a type of longitudinal study in which data are collected at two or more points in time from individuals in a cohort; cohort studies do not require random assignment of subjects, which in many cases is unethical. It is also highly flexible and can be used for either original or secondary data analysis; Cohort studies make it difficult to assess whether there are associations between the cohort and dependent variables and present threats to validity.