As longitudinal studies are observational, there will be no interference with the respondents or subjects if it happens to be a survey. They are unique from other types of research because of their timeline. This means that the same subjects are observed multiple times (often in the course of many years), instead of the researchers trying to collect data from various subjects with the aim to study the same variables. For psychologists, they prefer to use this method in measuring the impact of different therapeutic practices over time, usually taking a control group as their baseline.
Another prime example of a medical study that uses a longitudinal method is one that follows the same 100 individuals over the course of 4 years to measure the effect of an experimental pharmaceutical product. By using the same subjects, scientists and research personnel can allow for a measurable change over a certain period of time to be collected. Like any other type of research methodology, longitudinal studies definitely have certain disadvantages, while they have their obvious advantages. Here is a list of these limits:
List of Advantages of Longitudinal Studies
1. They can show clear variable patterns over time.
One key advantage of performing longitudinal studies is their ability to show patterns of a variable over time, which is a very powerful way through which researchers come to learn about the relationships of cause and effect. Depending on the scope of the research, longitudinal observation will also be able to help with discovering the “sleeper effects” or the connections between a variety of events over a long period of time, where events otherwise may not be linked.
2. They allow for clear focus and validity.
With a clear focus, longitudinal studies would see how a particular end state or a set of circumstances would come to be. And though people usually might not remember past events, it can be solved by means of actual recording, thus ensuring a high level of validity.
3. They can provide useful data.
A longitudinal study is unique in itself in terms of its ability to provide useful data about individual changes.
4. They have more power than cross-sectional studies.
As most longitudinal studies use the observation method (they observe the state of the world without manipulating it), it has been argued that they may have less power in detecting causal relationships than experiments. However, because of the repeated observations they use at individual levels, they have more power than cross-sectional observational studies in terms of being able to exclude time-invariant, unobserved individual differences and in terms of observing a certain event’s temporal order.
5. They are perfect for doing research on developmental trends.
A longitudinal study is often used in psychology in studying developmental trends across life spans and in sociology in studying life events throughout generations or lifetimes. This is primarily because, unlike a cross-sectional study, in which different individuals with same characteristics are compared, a longitudinal study would track the same people, thus the differences observed in the group will be less likely to be the result of a cultural difference across generations.
6. They ensure high accuracy when it comes to observation of changes.
Because they are perfect for doing research on developmental trends, longitudinal studies can make observation of changes more accurate, making them a more preferred method in various fields. In medicine, such a method is used to discover indicators or predictors of certain illnesses, while in advertising, it is used to identify changes that an ad campaign has produced in the behaviors and attitudes of people belonging to the target audience who have seen the advertisement.
7. They are flexible.
Longitudinal studies allow for flexibility to occur, which means their focus can be shifted while data is being collected.
List of Disadvantages of Longitudinal Studies
1. They drop out from a panel study.
One of the biggest drawbacks of performing longitudinal studies is panel attrition. If you are only depending on the same group of subjects for a study that takes place once in a while for years, some of these subjects will obviously no longer be able to participate due to various reasons, such as refusal, changes in contact information and death, which cuts down useable data that can be drawn for an ultimate conclusion.
2. They require enormous amounts of time.
Another huge drawback to any longitudinal study is the great amount of time it needs to collect all the data that is needed. Usually, it takes a long period of time to gather results before you can start making patterns.
3. They would gather data that is not that reliable.
While longitudinal data is collected at multiple points, these observation periods are pre-determined and cannot be taken into account no matter what happens between these points. Aside from this, there is also the idea of panel conditioning, where respondents can often unknowingly change their qualitative responses over time to better fit what they consider to be the intended goal of the observer. The process of longitudinal studies itself has changed how subjects or respondents view the questions used.
4. They require a large sample size.
This disadvantage means that such studies should have a large number of subjects who are willing to cooperate.
5. They can be costly compared to cross-sectional studies.
It is known that cross-sectional studies are more affordable compared to longitudinal studies. With fewer touch points, the former are also much quicker in reaching an observational conclusion. Considering they use a carefully chosen sample size, they can be more helpful in representing entire populations, instead of using subsets, which can be very beneficial when it comes to considering a policy change.
Many studies encourage and welcome the use of longitudinal datasets as a resource for further developments, where researchers are able to apply and access data through relevant pathways that are set out by the organizations holding such information. However, this technique also has its limitations. Based on the advantages and disadvantages that are listed above, do you think longitudinal studies are more helpful to advancing society, or not?
Brandon Miller has a B.A. from the University of Texas at Austin. He is a seasoned writer who has written over one hundred articles, which have been read by over 500,000 people. If you have any comments or concerns about this blog post, then please contact the Green Garage team here.