Longitudinal Research/Experience Sampling Technique

Types of Longitudinal Research

Five main types of longitudinal research study can be identified:

• 1.
  A trend study compares different groups from the same population at different points in time. It can provide information about net change but not individual change.
• 2.
  A panel study tracks the same individuals at fixed intervals over a period of time, which often covers many years.
• 3.
  A cohort study follows a sample of individuals from a particular group (e.g., an age or an employment group) at fixed intervals over a period of time. It is usually a form of panel study, but it becomes a trend study if a new sample is observed at each time point. A number of cohorts can be simultaneously observed and compared over time, which can be useful for separating the effects of maturational and external influences. For example, comparing different age cohorts measured at the same point in time and the same age cohorts measured at different points in time can help distinguish changes that normally occur as people get older from changes resulting from shifts in employment. If a cohort has received a treatment or intervention, the study is also a quasi-experiment because the individuals have not been assigned randomly to the groups being compared.
• 4.
  An intervention study—which is also a form of quasi-experiment—examines the effects of a naturally occurring intervention (e.g., occupational retirement) or an imposed intervention (e.g., a stress-prevention program) by comparing data collected from a group on one or more occasions, both before and after it receives the intervention. Collecting data at the same times from a comparison or control group that has not received the intervention can help to establish whether the changes resulted from the intervention.
• 5.
  An experience sampling study obtains reports from the same individuals on many occasions at frequent intervals. It is distinguished by its focus on individuals' immediate experiences in their natural environment and its high frequency of reporting.

Retrospective studies, in which participants recall aspects of their life histories or recent past, are sometimes also labeled longitudinal, but this is not strictly accurate because, although they cover periods of time, they do not usually involve real-time sampling at more than one time point. In genuinely [Page 464]longitudinal retrospective studies, participants report at consecutive time points on their experiences since the last time point. Prospective studies are often preferred, however, because they are less susceptible to the problem of memory recall.

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