DEFINITION of 'TTest'
A statistical examination of two population means. A twosample ttest examines whether two samples are different and is commonly used when the variances of two normal distributions are unknown and when an experiment uses a small sample size. For example, a ttest could be used to compare the average floor routine score of the U.S. women's Olympic gymnastic team to the average floor routine score of China's women's team.
INVESTOPEDIA EXPLAINS 'TTest'
The test statistic in the ttest is known as the tstatistic. The ttest looks at the tstatistic, tdistribution and degrees of freedom to determine a p value (probability) that can be used to determine whether the population means differ. The ttest is one of a number of hypothesis tests. To compare three or more variables, statisticians use an analysis of variance (ANOVA). If the sample size is large, they use a ztest. Other hypothesis tests include the chisquare test and ftest.

PTest
A statistical method used to test one or more hypotheses within ... 
Population
The entire pool from which a statistical sample is drawn. The ... 
ZTest
A statistical test used to determine whether two population means ... 
Simple Random Sample
A subset of a statistical population in which each member of ... 
Distribution
1. When trading volume is higher than that of the previous day ... 
Statistically Significant
The likelihood that a result or relationship is caused by something ...

Fundamental Analysis
Find The Right Fit With Probability Distributions
Discover a few of the most popular probability distributions and how to calculate them. 
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. 
Economics
Is the Bureau of Labor Statistics accurate?
Read this brief analysis of the accuracy of Bureau of Labor Statistics, including a summary of the types of reports issued and how they are compiled. 
Economics
Where is cost of living lowest in the world?
Learn how the cost of living is the lowest in India based on numbers derived from the CPI and organizations like Expatistan and Numbeo. 
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. 
Economics
How does the Bureau of Labor Statistics define contingent workers?
Discover how contingent workers are a significant part of the labor force and are defined as persons who do not expect their jobs to last. 
Economics
How does the Bureau of Labor Statistics determine the Consumer Price Index (CPI)?
Changes in the average price level of more than 200 goods and services across the U.S. economy are used to determine the Consumer Price Index, or CPI. 
Economics
How is the cost of living index calculated?
Discover how calculations for cost of living indexes are made based on the average prices of common goods and services between different regions. 
Economics
How does the Bureau of Labor Statistics determine the unemployment rate?
Learn how estimates of the unemployment rate are made based on monthly surveys of American households that are conducted by the U.S. Census Bureau.