Longitudinal Design and its Types

Longitudinal Design and its Types by Nauman Khan

1. Longitudinal Design and its Types Assigned by: Dr.zafar Iqbal Presented by: Nauman khan (MS-II)

2. Definition: A longitudinal study 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. Cohort studies are common in medicine, psychology and sociology, where they allow researchers to study changes over time.

3. Longitudinal Design: This study type is particularly useful for evaluating the relationship between risk factors and the development of disease, and the outcomes of treatments over different lengths of time. Similarly , because data is collected for given individuals within a predefined group, appropriate statistical testing may be employed to analyze change over time for the group as a whole, or for particular individuals

4. Longitudinal Design: A few key things to remember about longitudinal studies: They are observational in nature They are a type of  correlational research Longitudinal research is often contrasted with cross-sectional research Longitudinal research involves collecting data over an extended period, often years or even decades Cross-sectional research  involves collecting data at a single point in time

5. Dimensions of Longitudinal Design: Settings: Applied in ranging from Highly controlled laboratory to large scale national surveys. Time Scale: Can be measured from very short period of time to many years.

6. Dimensions of Longitudinal Design: Number of Time points: Varies in terms of How many times information is collected from the same set of people in panel study or different set of people in trend study. [ Trend Study: (Repeated Cross-sectional Study), entail collecting information from comparable samples overtime but not from the same people]. [Panel Study: it involves repeated surveys of the same people. It involve collecting data concerning at least two times points. Planned Interventions: Vary from planned interventions to naturally occurring events.

7. Purpose of Longitudinal Design: Describing Patterns of Change and stability. Establishing Temporal Order. Establishing developmental (Age) Effect. Establishing Historical (Period) Effect. Life Course “Career” analysis.

8. Types of Longitudinal Design: Panel Study:  Involves sampling a cross-section of individuals . Cohort Study:  Involves selecting a group based on a specific event such as birth, geographic location or historical experience . Retrospective Study:  Involves looking to the past by looking at historical information such as medical records.

9. Types of Longitudinal Design: Prospective Panel Design: “Prospective studies where the same participants are followed over a period of time”. 1. Simple Prospective Panel Design:- (requires the collection of data at two points of time from same sample). 2. Multiple Point Prospective Panel Design:- (similar to simple prospective but involves more data collection points). 3. Single Panel Design without replacement:- (the more points at which the data are collected and the longer the data of the study, the more dropouts become a problem). (Two problems: 1. Unacceptably small final sample, 2. Final sample can become unrepresentative which threatens external validity).

10. Types of Longitudinal Design: Prospective Panel Design: “Prospective studies where the same participants are followed over a period of time”. 4 . Single Panel Design with replacement:- (the more points at which the data are collected and the longer the data of the study, the replacement for sample dropouts to include new types of members to the sample). (sample size and representativeness is maintained). 5. Rotating Panel Design:- (systematic and randomized way of dealing with sample dropout and in so doing maximizes the external validity). (Frequently measure).

11. Types of Longitudinal Design: Prospective Panel Design: “Prospective studies where the same participants are followed over a period of time”. 4 . Single Cohort Design:- (involve selecting a group of similarly aged people at one point of time and following it over an extended period). 5. Multiple Cohort Design:- (Its main feature is the spread of cohorts. This spread permits comparisons between cohorts and thus helps distinguish between ageing and period effects). 6. Cohort Sequential Design:- (Its distinctive aspect is that over time cohorts drop out of the study).

12. Types of Longitudinal Design: Retr ospective Design: “ Involves looking to the past by looking at historical information such as medical records”. 1 . Retrospective Panel Design :- (it enables us to establish the sequence of events, which, in turn, enables us to make stronger assertions about causal order and causation). 2 . Record Linkage Design:- (It’s a design where data are collected from official records. Where these records have been collected overtime). 3 . Quasi-Longitudinal Design:- (It entails collecting data at different points of time so that changes can be plotted, but these data are collected from different individuals at each time point).

13. Types of Longitudinal Design: Retr ospective Design: “ Involves looking to the past by looking at historical information such as medical records”. 4 . Simulated Before-After Design :- ( entail measuring a group before and after an intervention and again afterward and hence the impact of intervention is estimated ). 5. Repeated cross-sectional Design:- (It’s obtaining the data over time that allows us to track the change at aggregate level).

14. Thank You!