What is a T-Test? What is a T-Test?
A T-Test is a statistical test used in determining if two different samples of data are similar or different from each other. Usually mean values are used from the two different sets of data and these are compared between each other and in relation to data variation and/or standard deviation of the difference between the two mean values involved. This type of test is commonly done with the null hypothesis stating that the mean values for the two different data samples or measures are equal.

The T-test as a statistical tool was introduced in the year 1908 by chemist named William S. Gosset. He was known then to have the pen name “Student”. This is why this test is also called as “Student’s T-Test”. He was working then for the Guiness brewery located in the city of Dublin in Ireland. He was tasked to use statistics in monitoring the quality of a type of dark beer called stout. With this task, he came up with the statistical method called T-Test.

The T-Test can be used when there are only two differing measurements or values to compare and when the data assignment is random. Two common types of this test can be employed namely: Independent-measures test and Matched-pair test. As the name implies, Independent-measures T-Test is the one used when data samples do not match while Matched-pair T-Test is employed when sample data appears to be in pairs.

A basic and easy application for T-Test is when a person just needs to compare sample data from a known standard value. Other common T-Test applications include those in one-sample location testing wherein the mean value of a sample population is compared with the value specified on the null hypothesis. Another T-Test that is frequently used is the testing of the null hypothesis involving two statistical values that are sourced from similar statistical units and has zero as the mean value.

In general terms, T-Tests may be useful when one is trying to compare values that are said to be “quantitative”. Quantitative values refer to data that can be measured like distance, speed, and temperature among others.

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