z-test

noun

ˈzē-ˌtest 

: any of several statistical tests that use a random variable having a z distribution to test hypotheses about the mean of a population based on a single sample or about the difference between the means of two populations based on a sample from each when the standard deviations of the populations are known or to test hypotheses about the proportion of successes in a single sample or the difference between the proportion of successes in two samples when the standard deviations are estimated from the sample data

Word History

First Known Use

1951, in the meaning defined above