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 ... 
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 ... 
LookAhead Bias
Bias created by the use of information or data in a study or ... 
Attribute Bias
The tendency of stocks selected by a quantitative technique or ... 
Survivorship Bias
The tendency for mutual funds with poor performance to be dropped ...

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. 
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 ... 
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. 
Investing Basics
Using Normal Distribution Formula To Optimize Your Portfolio
Normal or bell curve distribution can be used in portfolio theory to help portfolio managers maximize return and minimize risk. 
Technical Indicators
The Normal Distribution Table, Explained
The normal distribution formula is based on two simple parameters  mean and standard deviation 
Economics
Can Investors Trust Official Statistics?
The official statistics in some countries need to be taken with a grain of salt. Find out why you should be skeptical. 
Investing Basics
RSquared
Learn more about this statistical measurement used to represent movement between a security and its benchmark.