Longitudinal studies allow social scientists to distinguish short from long-term phenomena, such as poverty.
[citation needed] Cohort studies are one type of longitudinal study which sample a cohort (a group of people who share a defining characteristic, typically who experienced a common event in a selected period, such as birth or graduation) and perform cross-section observations at intervals through time.
[3] As opposed to observing an entire population, a panel study follows a smaller, selected group - called a 'panel'.
[5][failed verification] Longitudinal studies do not require large numbers of participants (as in the examples below).
[citation needed] Practice effect is also one of the problems: longitudinal studies tend to be influenced because subjects repeat the same procedure many times (potentially introducing autocorrelation), and this may cause their performance to improve or deteriorate.