<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A statistical test that is used to find out if there is a real difference between the means (averages) of two different groups. It is sometimes used to see if there is a significant difference in response to treatment between groups in a clinical trial.</n0:def-definition><n0:def-source>NCI-GLOSS</n0:def-source></n0:ComplexDefinition><n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A statistical test used to compare the means of two groups of test data.</n0:def-definition><n0:def-source>CDISC</n0:def-source></n0:ComplexDefinition>
<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A statistical hypothesis test based on a test statistic whose sampling distribution is a t-distribution. The term "t-test" is often used in a narrower sense: it refers to a popular test aimed at testing the hypothesis that the population mean is equal to some value m (see also t-statistic). The most popular t-tests are aimed at testing the following hypotheses: 1. The population mean is as hypothesized (the population variance is not known); 2. The means of two populations are equal (the population variances are not known but equal); 3. The means of two populations are equal (the population variances are not known and not equal); 4. The correlation coefficient for two random variables is zero; 5. The slope of the population regression line is zero.</n0:def-definition><n0:def-source>NCI</n0:def-source><n0:attr>Statistics.com Glossary</n0:attr></n0:ComplexDefinition>