To overcome some of the limitations of traditional developmental designs, investigators sometimes use sequential designs, in which they conduct several similar cross-sectional or longitudinal studies (called sequences). The sequences might study participants over the same ages but in different years, or they might study participants over different ages but during the same years. some sequential designs combine longitudinal and cross-sectional strategies, an approach that has three advantages:
We can find out whether cohort effects are operating by comparing participants of the same age who were born in different years. we can compare the longitudinal samples at ages 12, 13, and 14. If they do not differ, we can rule out cohort effects.
We can make both longitudinal and cross-sectional comparisons. If outcomes are similar, we can be especially confident about the findings.