# Cross-Sequential Study --- A **cross-sequential study** is a method of [[scientific research|study]] designed where the observers analyse data collected at regular time intervals, while simultaniously increaseing the sample size with younger cohorts in order to control for historical events that occur for each cohort. It is particularly useful in the study of [[life-span development]]. It is a combination of a **cross-sectional study** and a **longitudinal study**. A cross-sectional study looks at different age groups and compares them. It is fast and easy to do but cannot account for generational events that affect the development whole cohorts. A longitudinal study studies the same individuals at several intervals over the course of many years. This takes more time (for obvious reasons), and the subjects may drop out or even increasingly aware of the purpose or goals of the study, but it produces better results. Unfortunately, both cross-sectional and longitudial studies fail to account for the effects of historical changes or events. (For example, I can imagine that my cohort would be affected by 9/11 in ways that other cohorts would not be.) ![[cross-sequential study.png]] ___