DEFINITION of 'Longitudinal Data'
The process of collecting sample observations from a larger population over a given time period. Longitudinal data is used in statistical and financial studies.
Next Up
BREAKING DOWN 'Longitudinal Data'
The process of analyzing past return data for a given security is an example of using longitudinal data. By collecting daily, weekly or monthly return data, a financial analyst can determine past return trends, and calculate the stock's value at risk (VaR) using the historical method.
RELATED TERMS

Sample
A subset containing the characteristics of a larger population. ... 
Sampling
A process used in statistical analysis in which a predetermined ... 
Statistics
A type of mathematical analysis involving the use of quantified ... 
Sampling Distribution
A probability distribution of a statistic obtained through a ... 
Representative Sample
A subset of a statistical population that accurately reflects ... 
Population
The entire pool from which a statistical sample is drawn. The ...
Related Articles

Investing
How Does Sampling Work?
Sampling is a term used in statistics that describes methods of selecting a predefined representative number of data from a larger data population. 
Investing
What is Systematic Sampling?
Systematic sampling is similar to random sampling, but it uses a pattern for the selection of the sample. 
Investing
Explaining Standard Error
Standard error is a statistical term that measures the accuracy with which a sample represents a population. 
Investing
Understanding Statistics
Statistics provide the means to analyze data and then summarize it into a numerical form. 
Investing
Understanding the Simple Random Sample
A simple random sample is a subset of a statistical population in which each member of the subset has an equal probability of being chosen. 
Investing
Value at Risk (VaR)
Value at risk, often referred to as VaR, measures the amount of potential loss that could happen in an investment or a portfolio of investments over a given time period. 
Investing
What is a Representative Sample?
In statistics, a representative sample accurately represents the makeup of various subgroups in an entire data pool. 
Investing
Explaining the Central Limit Theorem
Central limit theorem is a fundamental concept in probability theory. 
Investing
How to Use Stratified Random Sampling
Stratified random sampling is a technique best used with a sample population easily broken into distinct subgroups. Samples are then taken from each subgroup based on the ratio of the subgroup’s ... 
Financial Advisor
How Big Data Has Changed Finance
The vast proliferation of data and increasing technological complexities continues to transform the way industries operate and compete.
RELATED FAQS

What percentage of the population do you need in a representative sample?
Learn about representative samples and how they are used in conjunction with other strategies to create useful data with ... Read Answer >> 
What's the difference between a representative sample and a convenience sample?
Learn the difference between convenience sampling and representative sampling and the advantages and disadvantages of each ... Read Answer >> 
How can a representative sample lead to sampling bias?
Learn how using representative samples alone is not enough to make sampling bias negligible and why elements such as randomization ... Read Answer >> 
How do researchers ensure that a simple random sample is an accurate representation ...
Learn which methods researchers employ to ensure that a simple random sample best approximates the larger population being ... Read Answer >> 
What's the difference between a representative sample and a random sample?
Explore the differences between representative samples and random samples, and discover how they are often used in tandem ... Read Answer >> 
What are the advantages of using a simple random sample to study a larger population?
Learn how simple random sampling works and what advantages it offers over other sampling methods when selecting a research ... Read Answer >>