Why can longitudinal studies be problematic?

Longitudinal studies are those which are carried out over a long period of time. Longitudinal studies can be problematic because, over time, participants may drop out. This is an issue because it leaves the experimenter with a reduced sample size, meaning that the results may be less generalisable to the general target population.

This is called attrition. Throw in this word and the examiner will be impressed.

In an essay, you can use this as a negative evaluation of a particular study.

For example, you could structure the paragraph this way:

-Say that an issue with the study is that it is longitudinal

-Explain what a longitudinal study is

-Give evidence of this (how long was the study?)

-Say that this may leave the study vulnerable to attrition

-Note how many participants were in the study (if you know) and explain that this number may diminish overtime as participants drop out

-Explain the affect that this may have on the results (less generalisable)

It might be good to put such a paragraph as this after a paragraph praising the study for having a large number of participants, or else a paragraph praising the volume of data that can be gained from a longitudinal study.