DEFINITION of 'Sample'
A subset containing the characteristics of a larger population. Samples are used in statistical testing when population sizes are too large for the test to include all possible members or observations. A sample should represent the whole population and not reflect bias toward a specific attribute.
INVESTOPEDIA EXPLAINS 'Sample'
A sample is a smaller, manageable version of a larger group. For example, if you wanted to test an investment strategy on past stock data, you would have an enormous number of stocks to test. Instead of testing the strategy on every stock, you would use a sample, which allows you to draw statistical insights from a smaller group of stocks. The sample should not contain any bias, such as the survivorship bias, where you might only use stocks that have survived the entire length of time you wish to test. Choosing a sample randomly should eliminate the possibilities of bias.

Sampling Distribution
A probability distribution of a statistic obtained through a ... 
LookAhead Bias
Bias created by the use of information or data in a study or ... 
Sampling Error
A statistical error to which an analyst exposes a model simply ... 
Normal Distribution
A probability distribution that plots all of its values in a ... 
Survivorship Bias
The tendency for mutual funds with poor performance to be dropped ... 
Attribute Bias
The tendency of stocks selected by a quantitative technique or ...

Bonds & Fixed Income
Find The Highest Returns With The Sharpe Ratio
Learn how to follow the efficient frontier to increase your chances of successful investing. 
Active Trading Fundamentals
Bet Smarter With The Monte Carlo Simulation
This technique can reduce uncertainty in estimating future outcomes. 
Active Trading
Modern Portfolio Theory: Why It's Still Hip
See why investors today still follow this old set of principles that reduce risk and increase returns through diversification. 
Markets
A Guide To Conference Board Indicators
Learn to put the CB data sets to trading use. Each chapter takes you through one of the board's benchmark indicators or surveys, their significance and their applications. 
Fundamental Analysis
What are the most common issues with Serial Correlation in stocks?
Read about the concept of serial correlation in stock returns, and learn why market analysts are divided about the efficacy of trading based on stock patterns. 
Trading Strategies
How far back in a stock's history should you go when gauging its volatility?
Discover why it can be difficult for investors to figure out how far back to go into a stock's history when gauging its volatility. 
Trading Strategies
What are common examples of Serial Correlation in finance?
Take a deeper look at serial correlation in finance, and find out why most attempts at discovering serial correlation among asset prices have failed. 
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 ... 
Personal Finance
What is the average salary for an accountant?
Learn about the average salaries of various accounting positions, and see the difference that an accounting degree makes in attaining higher wages. 
Fundamental Analysis
Lognormal and Normal Distribution
When and why do you use lognormal distribution or normal distribution for analyzing securities? Lognormal for stocks, normal for portfolio returns.