title: Statistical considerations for cross-sectional data relating to tracheal reconstruction over time.
abstract: Complementary statistical analyses are performed on data concerning tracheal reconstruction in rats. The principal response criterion is vessel area as defined by the area of a graft onto the trachea covered by blood vessels. Postoperatively, this vessel area changes in a nonlinear fashion over time. Starting at 0% immediately postoperation, the vessel area increases to a peak and then sharply decreases to a certain level at which it remains. A total of 64 independently observed cross-sectional pairs (postop day, vessel area) are distributed among four treated groups. Analysis consists of two-way analysis of variance and piecewise linear regression under the usual assumptions of normality and variance homogeneity. Other analyses that relax these assumptions are also considered; treatment differences are established by nonparametric tests, and a quasi-likelihood analysis of the piecewise linear regression model is applied under the assumption of a binomial-like variance function. The resulting fit of the normal-theory-based piecewise linear model is compared to that of a nonlinear model whose shape is that of a gamma function integrand.
authors.affiliation: Department of Biostatistics, School of Public Health, University of North Carolina, Chapel Hill 27599-7400.
authors.forename: J S
authors.initials: JS
authors.lastname: Preisser
authors.forename: G G
authors.initials: GG
authors.lastname: Koch
authors.forename: W W
authors.initials: WW
authors.lastname: Shockley
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D003430:Cross-Sectional Studies; D003627:Data Interpretation, Statistical; D016013:Likelihood Functions; D016014:Linear Models; D015233:Models, Statistical; D051381:Rats; D012044:Regression Analysis; D014132:Trachea / Q000503:physiopathology*