DEFINITION of 'ZTest'
A statistical test used to determine whether two population means are different when the variances are known and the sample size is large. The test statistic is assumed to have a normal distribution and nuisance parameters such as standard deviation should be known in order for an accurate ztest to be performed.
INVESTOPEDIA EXPLAINS 'ZTest'
A onesample location test, twosample location test, paired difference test and maximum likelihood estimate are examples of tests that can be conducted as ztests. Ztests are closely related to ttests, but ttests are best performed when an experiment has a small sample size. Also, ttests assume that the standard deviation is unknown, while ztests assume that it is known. If the standard deviation of the population is unknown, the assumption that the sample variance equals the population variance is made.

PTest
A statistical method used to test one or more hypotheses within ... 
TTest
A statistical examination of two population means. A twosample ... 
Adjusted Mean
Statistical averages that have been corrected to compensate for ... 
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 ...

Investing Basics
Breaking Down The Geometric Mean

Bonds & Fixed Income
Accelerating Returns With Continuous ...

Fundamental Analysis
Calculating Covariance For Stocks