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ROBUST PROCEDURES FOR ANALYSING A TWO‐PERIOD CROSS‐OVER DESIGN WITH BASELINE MEASUREMENTS
Author(s) -
TSAI K. T.,
PATEL H. L.
Publication year - 1996
Publication title -
statistics in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.996
H-Index - 183
eISSN - 1097-0258
pISSN - 0277-6715
DOI - 10.1002/(sici)1097-0258(19960130)15:2<117::aid-sim158>3.0.co;2-b
Subject(s) - wilcoxon signed rank test , baseline (sea) , statistics , bivariate analysis , parametric statistics , normality , mathematics , regression , univariate , regression analysis , econometrics , computer science , multivariate statistics , mann–whitney u test , oceanography , geology
Patel analysed a two‐period cross‐over design with baseline measurements assuming bivariate normality for the joint distribution of the period responses. In this paper, we propose non‐parametric methods for analysing this design, including the use of the Wilcoxon rank sum test to derive the preliminary tests from the baseline measurements. We fit a robust regression line of the treatment response on baseline for each period and compute residuals. We also fit a robust locally weighted regression as an alternative method for computing residuals. Then, following Koch's procedure, we analyse the residuals for testing the significance of the treatment × period interaction and the treatment difference. We provide a numerical example to illustrate the methods.