title: [Clinical research XV. From the clinical judgment to the statistical model. Difference between means. Student's t test].
abstract: Among the test to show differences between means, the Student t test is the most characteristic. Its basic algebraic structure shows the difference between two means weighted by their dispersion. In this way, you can estimate the p value and the 95 % confidence interval of the mean difference. An essential feature is that the variable from which the mean is going to be calculated must have a normal distribution. The Student t test is used to compare two unrelated means (compared between two maneuvers), this is known as t test for independent samples. It is also used to compare two related means (a comparison before and after a maneuver in just one group), what is called paired t test. When the comparison is between more than two means (three or more dependent means, or three or more independent means) an ANOVA test (or an analysis of variance) it is used to perform the analysis.
authors.affiliation: Centro de Adiestramiento en Investigación Clínica, Coordinación de Investigación en Salud, Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, Distrito Federal, México, Mexico. rivasrodolfo@gmail.com.
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Rivas-Ruiz
authors.forename: Marcela
authors.initials: M
authors.lastname: Pérez-Rodríguez
authors.forename: Juan O
authors.initials: JO
authors.lastname: Talavera
mesh_terms: D000704:Analysis of Variance; D035843:Biomedical Research; D007600:Judgment; D015233:Models, Statistical
keywords: ANOVA; normal distribution; statistics; t test