The Two-Sample t-Test and Randomization Test
ثبت نشده
چکیده
Many Six Sigma practitioners use “Student’s” independent two-sample t-test when investigating differences in means. This type of test is based upon drawing random samples from two independent normal (Gaussian) distributions. Often, however, the assumption of normality and/or random sampling is violated. This article discusses when and why the two-sample t-test may be considered robust to these assumptions by comparing t-test results to randomization test results.
منابع مشابه
Asymptotic Properties of a Two Sample Randomized Test for Partially Dependent Data
We are concerned with an issue of asymptotic validity of a non-parametric randomization test for the two sample location problem under the assumption of partially dependent observations, in which case the validity of the usual permutation t-test breaks down. We show that a certain modification of the permutation group used in the randomization procedure yields an unconditional asymptotically va...
متن کاملPower comparison of non-parametric tests: Small-sample properties from Monte Carlo experiments*
Non-parametric tests that deal with two samples include scores tests (such as the Wilcoxon rank sum test, normal scores test, log istic scores test, Cauchy scores test, etc.) and Fisher’s randomization test. B ecause the non-parametric tests generally require a large amount of computational work, there are few studies on small-sample properties, although asymptotic properties with regard to var...
متن کاملA Closer Look at Testing the “No-Treatment-Effect” Hypothesis in a Comparative Experiment1
Standard tests of the “no-treatment-effect” hypothesis for a comparative experiment include permutation tests, the Wilcoxon rank sum test, two-sample t tests, and Fisher-type randomization tests. Practitioners are aware that these procedures test different no-effect hypotheses and are based on different modeling assumptions. However, this awareness is not always, or even usually, accompanied by...
متن کاملTeaching Random Assignment: Do You Believe It Works?
Textbook authors admonish students to check on the comparability of two randomly assigned groups by conducting statistical tests on pretest means to determine if randomization worked. A Monte Carlo study was conducted on a sample of n = 2 per group, where each participant's personality profile was represented by 7,500 randomly selected and assigned scores. Independent samples t tests were condu...
متن کاملتأثیر آموزش مدیریت زمان بر تعارض کار - زندگی در پرستاران
Background & Aim: The present research attempted to investigate the effect of time management training on work-life conflict among two hospitals;apos nurses. Methods & Materials: In this randomized trial, we recruited all nurses of two public hospitals (n=106) in Hamadan and Tehran according to the inclusion criteria. We used balanced (permuted) block randomization for assigning the study samp...
متن کامل