The term longitudinal study refers to the research condition when there are no interferences with the respondents or subjects. In other words, the researcher need not be collecting data based from a variety of respondents to get the variables required. Instead, only the same subjects are being observed a number of times in a particular period.
For psychologists, they use longitudinal studies so they can determine the impact of different therapy practices in time. They often use a control group to be their base line. The same goes for medical studies in which they might get a hundred people to measure the impact of experimental drugs. Thus, they can measure some changes over a period that they can collect.
List of Strengths of Longitudinal Study
1. It Shows Variable Patterns Over Time
The advantage of using longitudinal study is that researchers can determine the patterns regarding a variable in a particular length of time. This is a good way to learn more about relationships having cause-and-effect. Likewise, longitudinal observations might also provide information about connections between various events over a period of time to determine links of events.
2. Provide Clear Validity and Focus
A longitudinal study can provide a clear focus on the outcome or circumstance that will happen. Despite the fact that people can forget the past, this issue can be solved using the actual recording to ensure a great level of validity.
3. More Powerful than Cross-Sectional Studies
Longitudinal studies work to observe the state of the situation without controlling it. But it was argued that these studies can be less influential to detect causal relationships compared to conducting experiments. Nevertheless, the observation made repeatedly at individual levels can be more influential than cross-sectional studies. This is because it can disregard time-invariance as well as unobserved differences.
List of Weaknesses of Longitudinal Study
1. Possibility of Panel Attrition
One disadvantages of longitudinal study is the occurrence of panel attrition. Say for instance, you have two thousand respondents of a study taking place annually, then you cover roughly twenty years for that particular research to end. Consequently, there is a possibility that some of the subjects will no longer be able to continue due to reasons of death, refusal or relocation for some. This will lessen the usable data for drawing conclusions.
2. Difficulty of Acquiring Data at Multiple Points
The fact that longitudinal data are collected between multiple points, the study will still remain even if something happened to any of the points within that particular timeframe. So regardless of the event that might have caused a different result, the study follows what was pre-determined.
3. Panel Conditioning Issues
The qualitative responses of the subjects can often change unknowingly to conform to the intended goal of the observer. This can happen over the intended period of time. For this reason, the process of the study has modified the way respondents view the questions.
Nowadays, there are many researches that adopt the use of longitudinal studies as resources to bring about further developments. But it can also have limits based on the strengths and weaknesses mentioned here.