This a type of survey method that involves repeated interviews of a group of people over a specific period of time. It is used to track progress or evolution over time. In other words, when you study Net Profit Margin (NPM) of banks (Say 4 banks) over a period of time (2018 -2020)
You data will look like this:
Banks
Time
NPM
FCMB
2020
50%
FCMB
2019
55%
FCMB
2018
51%
First Bank
2020
60%
First Bank
2019
70%
First Bank
2018
55%
Fidelity Bank
2020
45%
Fidelity Bank
2019
50%
Fidelity Bank
2018
60%
Zenith Bank
2020
80%
Zenith Bank
2019
70%
Zenith Bank
2018
75%
Longitudinal Survey
It is another word used to describe panel survey. It refers to any study that examines the same group of people over a period of time.
Cross-sectional survey.
This is refers to data collected by observing many subjects such as individuals, firms, countries at the same point in time or without regard to differences in time. Here data is obtained at a particular point in time. The analysis of cross-sectional data usually consists of comparing the differences among the subjects. For example, if you are studying the net profit margin (NPM) of four banks in 2020 only. You will have a data that look like this:
Banks
Time
NPM
FCMB
2020
50%
First Bank
2020
60%
Fidelity Bank
2020
45%
Zenith Bank
2020
80%
This is what we called cross sectional data study since you are studying Banks at a particular point in time (2020).
