To test or not to test

• Verfasst von: Rochon, Justine [VerfasserIn]
• Verfasst von: Gondan, Matthias [VerfasserIn]
• Verfasst von: Kieser, Meinhard [VerfasserIn]
• Titel: To test or not to test
• Titelzusatz: preliminary assessment of normality when comparing two independent samples
• Verf.angabe: Justine Rochon, Matthias Gondan and Meinhard Kieser
• E-Jahr: 2012
• Jahr: 19 June 2012
• Fussnoten: Gesehen am 16.07.2018
• Titel Quelle: Enthalten in: BMC medical research methodology
• Ort Quelle: London : BioMed Central, 2001
• Jahr Quelle: 2012
• Band/Heft Quelle: 12(2012) Artikel-Nummer 81, 11 Seiten
• ISSN Quelle: 1471-2288
• DOI: doi:10.1186/1471-2288-12-81
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: Mann-Whitney’s U test
• Sach-SW: Student’s t test
• Sach-SW: Testing for normality
• K10plus-PPN: 1577645049

Abstract

Student’s two-sample t test is generally used for comparing the means of two independent samples, for example, two treatment arms. Under the null hypothesis, the t test assumes that the two samples arise from the same normally distributed population with unknown variance. Adequate control of the Type I error requires that the normality assumption holds, which is often examined by means of a preliminary Shapiro-Wilk test. The following two-stage procedure is widely accepted: If the preliminary test for normality is not significant, the t test is used; if the preliminary test rejects the null hypothesis of normality, a nonparametric test is applied in the main analysis.