Psychology Longitudinal Research vs Cross Sectional

Longitudinal Research

is an observational research method in which data is gathered for the same subjects repeatedly over a period of time. Longitudinal research projects can extend over years or even decades. In a longitudinal cohort study, the same individuals are observed over the study period.

Cross Sectional

is a type of observational study that analyzes data collected from a population, or a representative subset, at a specific point in time

Cross Sectional Advantages

- Used to prove and/or disprove assumptions - Not costly to perform and does not require a lot of time - Captures a specific point in time - Contains multiple variables at the time of the data snapshot - The data can be used for various types of research - Many findings and outcomes can be analyzed to create new theories/studies or in-depth research

Longitudinal Advantages

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.

Longitudinal Disadvantages

Longer time needed People lose interest People pass away 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.

Cross Sectional Disadvantages

Never see results Cannot be used to analyzed behavior over a period to time Does not help determine cause and effect The timing of the snapshot is not guaranteed to be representative Findings can be flawed or skewed if there is a conflict of interest with the funding source May face some challenges putting together the sampling pool based on the variables on the population being studied.