Longitudinal studies are a method of observational research. In this type of study, data is gathered from the same subjects repeatedly over a defined period. Because of this structure, it is possible for a longitudinal study to last for several years or even several decades. This form of research is common in the areas of sociology, psychology, and medicine.
The primary advantage of using this form of research is that it can help find patterns that may occur over long periods, but would not be observed over short periods. Changes can be tracked so that cause and effect relationships can be discovered.
The primary disadvantage of using longitudinal studies for research is that long-term research increases the chances of unpredictable outcomes. If the same people cannot be found for a study update, then the research ceases.
Here are some additional key advantages and disadvantages of longitudinal studies to think about.
What Are the Advantages of Longitudinal Studies?
1. It allows for high levels of validity.
For a long-term study to be successful, there must be rules and regulations in place at the beginning that dictate the path that researchers must follow. The end goal of the research must be defined at the beginning of the process as well, with outlined steps in place that verify the authenticity of the data being collected. This means high levels of data validity are often available through longitudinal studies.
2. The data collected is unique.
Most research studies will collect short-term data to determine the cause-and-effect of what is being researched. Longitudinal studies follow the same principles, but extend the timeframe for data collection on a dramatic scale. Long-term relationships cannot be discovered in short-term research, but short-term relationships can be tracked in long-term research.
3. Most will use the observational method.
Because longitudinal studies will use the observational method for data collection more often than not, it is easier to collect consistent data at a personal level. This consistency allows for differences to be excluded on a personal level, making it easier to exclude variations that could affect data outcomes in other research methods.
4. It makes it possible to identify developmental trends.
Whether in medicine, psychology, or sociology, the long-term design of a longitudinal study makes it possible to find trends and relationships within the data collected. It isn’t just the span of a human life that can be tracked with this type of research. Multiple generations can have real-time data collected and analyzed to find trends. Observational changes can also be made from past data so it can be applied to future outcomes.
5. Data collection accuracy is almost always high.
Because data is collected in real-time using observational data, the collection process is almost always accurate. Humans are fallible beings, so mistakes are always possible, but the structure of this research format limits those mistakes. That data can also be used to implement necessary changes that a course of action may need to take so the best possible outcome can be identified.
6. Longitudinal studies can be designed for flexibility.
Although a longitudinal study may be created to study one specific data point, the collected data may show unanticipated patterns or relationships that may be meaningful. Because this is a long-term study, there is a flexibility available to researchers that is not available in other research formats. Additional data points can be collected to study the unanticipated findings, allowing for shifts in focus to occur whenever something interesting is found.
What Are the Disadvantages of Longitudinal Studies?
1. There is a factor of unpredictability always present.
Because longitudinal studies involve the same subjects over a long period, what happens to them outside of the data collection moments can influence future data being collected. Some people may choose to stop participating in the research. Others may no longer find themselves in the correct demographics for the research. If these factors are not included in the initial design of the research, then it could invalidate the findings that are produced.
2. It takes time.
Researchers involved with longitudinal studies may never see the full outcome of their work. It may take several years before the data begins producing observable patterns or relationships that can be tracked. That means the ability to maintain open lines of communication with all researchers is vitally important to the eventual success of the study.
3. The data gathered by longitudinal studies is not always accurate or reliable.
It only takes one piece of unreliable or inaccurate data to possibly invalidate the findings that the longitudinal studies produce. Because humans have their own personal bias toward certain subjects, the researcher processing the data may unconsciously alter the data to produce intended results.
4. It relies on the skills of the researchers to be complete.
Because data collection occurs in real-time and relies heavily on the skills of the researchers who are tasked with this job, the quality of the data is heavily reliant on those skills. Two different researchers with varying skill levels can produce very different data points from the same subject material. Personal views of the data being collected can also impact the results on both ends, from the subject or the collector.
5. Large sample sizes are required to make the research meaningful.
To develop relationships or patterns, a large amount of data must be collected and then mined to create results. That means a large sample size is required so the amount of data being collected can meet expectations. When the subjects being studied are people, it can be difficult to find enough people who are willing to honestly participate in the longitudinal studies.
6. There is a direct cost that is higher than other forms of research.
Longitudinal research requires a larger sample size, which means there is a larger cost involved in contacting subjects to collect data. It is also a long-term form of research, which means the costs of the study will be extended for years, or decades, when other forms of research may be completed in a fraction of that time.
7. One person can change a long-term outcome.
Because there is such a reliance on individual interpretations within longitudinal studies, it is possible for one person to inadvertently alter or invalidate the data being collected. It is entirely possible for decades of research to be invalidated because one subject or researcher was misleading.
The advantages and disadvantages of longitudinal studies show us that there is a tremendous value available in the ability to find long-term patterns and relationships. If the unpredictable factors of this research format can be planned for in advance and steps taken to remove bias, the data collected offers the potential to dramatically change the fields of medicine, psychology, or sociology.
About the Author of this Article
Natalie Regoli is a seasoned writer, who is also our editor-in-chief. Vittana's goal is to publish high quality content on some of the biggest issues that our world faces. If you would like to contact Natalie, then go here to send her a message.