Longitudinal studies vs. cross-sectional studies

Cross-sectional studies are discrete studies that capture data within a particular context at a particular point in time. These kinds of studies are more appropriate for research inquiries that don’t examine some form of development or evolution, such as concepts or phenomena that are generally static or unchanging over extended periods of time.

To determine which type of study would be more appropriate for your research inquiry, it’s important to identify the object of inquiry that is being studied. Ask yourself the following questions when planning your study:

Do you need an extended period of time to sufficiently capture the phenomenon?
Is the sample of data collected likely to change over time?
Is it feasible to commit time and resources to an extended study?

If you said yes to all of these questions, a longitudinal study would be suited to addressing your research questions. Otherwise, cross-sectional studies may be more appropriate for your research.

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Benefits of longitudinal studies

A longitudinal study can provide many benefits potentially relevant to the research question you are looking to address. Here are three different advantages you might consider.

Abundance of data

In many cases, research rigor is served by collecting abundant data. Research approaches like thematic analysis and content analysis benefit from a large set of data that helps you identify the most frequently occurring phenomena within a research context. Large data sets collected through longitudinal studies can be useful for separating abundance from anecdotes.

Identification of patterns

Analyzing patterns often implies exploring how things interact sequentially or over time, which is best captured with longitudinal data. Think about, for example, how sports competitions and political elections take place over a year or even multiple years. Construction of ships and buildings can be a long and protracted process. Doctoral students can spend four or more years before earning their degree. A simple cross-sectional study in such contexts may not gather sufficient data captured over a period of time long enough to observe sequences of related events.

Observation of relationships

Certain relationships between different phenomena can only be observed longitudinally. The famous marshmallow test that asserted connections between behaviors in childhood and later life outcomes spawned decades of longitudinal study. Even if your research is much simpler, your research question might involve the observation of distant but related phenomena that only a longitudinal study can capture.

Types of longitudinal studies

There are two types of longitudinal studies to choose from, primarily depending on what you are looking to examine. Keep in mind that longitudinal study design, no matter what type of study you might pursue, is a matter of sustaining a research inquiry over time to capture the necessary data. It’s important that your decision-making process is both transparent and intentional for the sake of research rigor.

Cohort studies

A cohort study examines a group of people that share a common trait. This trait could be a similar age group, a common level of education, or a shared experience.

An example of a cohort study is one that looks to identify factors related to successful aging found in lifestyles among people of middle age. Such a study could observe a group of people, all of whom are similar in age, to identify a common range of lifestyles and activities that are applicable for others of the same age group.