The longitudinal method examines one group of people repeatedly over time, whereas the cross-sectional method examines several groups of people at one point in time. For example, if you investigated changes in social behavior in 20-, 30-, and 40-yearolds all measured at one point in time, you would be conducting a cross-sectional research study. In other words, cross-sectional studies examine age differences, while longitudinal studies measure age changes.
As with the longitudinal approach, the cross-sectional approach has its advantages and disadvantages. Advantages are that it is relatively inexpensive in that it usually does not take a long time to complete, it takes place over a relatively short span of time so it is easier for participants to cooperate, it has a low dropout rate since it does take place over shorter period of time, and problems with staff retention are minimized since turnover is greatly reduced.
Cross-sectional research designs have their disadvantages as well. For example, it makes comparisons of groups difficult since all the data are collected at one point in time, it provides little idea as to the direction of change that a group might take (there are no previous data as in a longitudinal study), it examines people of the same chronological age who may be of different maturational levels, and reveals nothing about the continuity of development on an individual basis. The most serious disadvantage is the lack of comparability of groups, because the only thing they differ on is age.
Finally, cross-sectional research strategies suffer since cohort (the year in which participants are born) and age are confounded, meaning that the effects of the two cannot be separated. One does not know whether any age-related changes are in fact a function of changes in age versus a difference in the years in which the participants were born. Even with these shortcomings, along with longitudinal research designs, cross-sectional research designs are very popular.
- MacFadven, , Hastings, G., & Mackintosh, A. M. (2001). Cross sectional study of young people’s awareness of and involvement with tobacco marketing. British Medical Journal, 322, 513–517.
- Salkind, (2005). Exploring research (6th ed.). Upper Saddle River, NJ: Prentice-Hall.