Longitudinal Research Design: Methods and Examples

What Is a Longitudinal Study: Definition

Let’s define ‘longitudinal study’ to begin with. This is an approach when data from the same respondents’ group is gathered repeatedly over a period of time. The reason why the same individuals are continuously observed over an extended period is to find changes and trends which can be analyzed.

This approach is essentially observational as you aren’t expected to influence the group’s parameters you are monitoring in any way. It is typically used in scope of correlational research which means collecting data about variables without assuming any dependencies. Let’s find out more about its usage and how much time it could take.

How Long Are Longitudinal Studies?

How long is a longitudinal study? It depends on your topic and research goals. In case characteristics of the subject are changing fast, it might be enough to take just a few measurements one by one. Otherwise, one might have to wait for a long time before measuring again.

So, such projects can take weeks or months but they also can extend over years or even decades. Studies like that are common in medicine, psychology and sociology, where it is important to observe how participants’ characteristics evolve.

How to Perform Longitudinal Research?

Before actively engaging in longitudinal research, it is important to understand well what your next steps should be. Let’s define study subtypes that can be used for such research. They are:

• Collecting and analyzing your own data.
• Finding data already collected by some other researcher and analyzing it.

Each of these subtypes has certain pros and cons. Gathering data yourself usually gives more confidence but it might be hard to contact the right individuals. Let’s discuss each point in detail. Likewise, you can pay someone to write my research paper.

Longitudinal Study: Data From Other Sources

When doing longitudinal studies of a certain group over a long period, you might find available data about them left from other researchers. Make sure to carefully examine sources of each dataset you decide to reuse. Otherwise previous researchers’ mistakes or bias may influence your results after you’ve analyzed that data.

However this approach could be very efficient in case the subject has already been investigated by different researchers. Their results could be compared and gaps or bias could be easier to eliminate. As a result, much time and effort could be saved.

Longitudinal Design: Own Data

When doing longitudinal studies without any significant predecessors’ works available, using your own data is the only reasonable way. This data is collected through surveys, measurement or observations. Thus you have more confidence in these results however this approach requires more time and effort. You need proper research design methods prior to starting the collection process.

If you choose such an approach, keep in mind that it has two major subtypes:

• retrospective research: collecting data about past events.
• prospective research: observing ongoing events, making measurements in more or less real time.

Longitudinal Study Types

A longitudinal study can be applied to a wide range of cases. You need to adjust your approach, depending on a specific situation, subject’s peculiarities and your research goals.  There are three major research types you can use for continuous observation:

1. Longitudinal Cohort Study
2. Retrospective Longitudinal Study
3. Longitudinal Panel Study

Let’s take a closer look at each type’s definition with our coursework writing service. Dive deep to learn how data is collected and what impact is made on results.

Longitudinal Cohort Study

A cohort longitudinal study involves selecting a group based on some unique event which unifies them all. It can be their birth date, geographic location, or historical experience. So there are special relationships between that group’s members which play significant roles for the entire research process.

Such a peculiarity is to be carefully selected when doing test design and planning your test steps. Sometimes one unifying event may be more relevant or convenient than another.

Retrospective Longitudinal Study

This approach takes a special place among longitudinal studies as it involves conducting some historical investigations. As we’ve already mentioned above, during a retrospective, researchers have to make observations and measurements of past events. Collecting historical data and analyzing changes might be easier than tracking live data. However the development of such research design must include checking the credibility of datasets that were used for it.

Longitudinal Panel Study

A panel study involves sampling a cross-section of individuals. This approach is often used for collecting medical data. Such a study when performed continuously is considered more reliable compared to a regular cross sectional study and allows using smaller sample sizes, while still being representative. However, there are various problems that may occur during such studies, especially those which go on for decades. Particularly, such samples can be eventually eroded because of deaths, migration, fatigue, or even by development of response bias.

Longitudinal Research Design

Longitudinal study design requires some serious planning to complete it properly. Keep in mind that your purpose is to directly address some individual change and variation cases. The target population should be chosen carefully so that results achieved through this study would be accurate enough.

Another key element is deciding about proper timing. For example you would need bigger intervals to ensure you detect important changes. At the same time, dissertation writers suggest that the intervals shouldn’t be too big. Otherwise, you might lose track of the actual trends within your target population.

Advantages and Disadvantages of Longitudinal Study

Let’s review longitudinal study advantages and disadvantages. Better wrap your head around this information if you are still choosing an optimal approach for your own project. Any study that involves complicated planning and extensive techniques can have some downsides. It is common for them to come together with benefits. So pay close attention to the information below before deciding what method to choose to observe your research subject.

Advantages of Longitudinal Study

These are the benefits of longitudinal study:

• it can provide unique insight that might not be available any other way. Particularly, it is the only way to investigate lifespan issues. It allows researchers to track changes across the entire generation. Let’s suppose the task is to track the percentage of farms which pass from parents to children in a certain location. Obtaining such information requires using historical records.
• such observational approach shows dynamics in respondent’s data and thus allows to model trends and understand their influence. Collecting data once provides only a snapshot of your group’s current state. Doing it continuously allows you to observe this group from some new angles. For example, you would get more information about your respondents’ habits if you observe them at least several times.

Longitudinal Study Disadvantages

This is the disadvantages of longitudinal study:

• it can be quite expensive since numerous repeated measurements require enormous amounts of time and effort. Imagine you need to collect data about a certain group for 10 years. Processing this data alone would require a lot of resources.
• such high costs may induce another problem: researchers might decide to use lesser samples in order to cut the expenditures. Consequently, results of such studies may not be representative enough.
• its participants tend to drop out eventually. The reasons may vary: moving to another location, illness, death or just loss of motivation to participate further. As a result, a sample is shrinking and thus decreasing the amount of data collection in research. This process is called selective attrition. A typical example is observing the life of some neighborhood in a big city: numerous people would move in and out so it would be hard to find a single individual who is available for a long time.

Longitudinal Study Examples

Let’s review some longitudinal study example which would be helpful for illustrating the above information.

Longitudinal research example

A famous longitudinal case is The Terman Study of the Gifted also known previously as Genetic Studies of Genius. Its founder and the main researcher, Lewis Terman, aimed to investigate how highly intelligent children developed into adulthood. He was also going to disprove the then-prevalent belief that gifted children were typically delicate physically and also socially inept. Initial observations began in 1921, at Stanford University. Eventually it led to confirming that gifted children were not significantly different from their peers in terms of physical development and social skills.

The results of this study were still being compiled during the 2000s which makes it the oldest and longest-running longitudinal study in the world. Such a huge period of data collection made it possible to obtain some really unique knowledge, not only about children’s development but about the history of education as well.

Longitudinal: Final Thoughts

In this article we’ve explored the longitudinal research notion and reviewed its main characteristics:

• conducting observations and measurements continuously over a long period of time
• some particular new insights which can be obtained by prolonged studies
• prospective advantages and disadvantages for researchers.