title: Modelling lactation using an inverse polynomial in a multilevel statistical model.
abstract: A method is outlined for modelling the relationship between breast-milk production and time from delivery, suitable for data collected longitudinally. The relationship is described using inverse polynomials. In a two-level model the coefficients are specified as random variables across subjects, allowing within- and between-subject variation to be separately estimated. In a three-level model, day-to-day variation can also be separately estimated. The model is illustrated using data from the Chiang Mai Lactation Project. It allows the use of covariates that vary over time, and provides a method of analysis that is compatible with the practical constraints on the timing of data collection that are inherent in longitudinal studies.
authors.affiliation: Department of Psychology, University of Durham, U.K.
authors.forename: R F
authors.initials: RF
authors.lastname: Drewett
authors.forename: H
authors.initials: H
authors.lastname: Goldstein
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D003627:Data Interpretation, Statistical; D036861:Delivery, Obstetric; D004034:Diet Surveys; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007774:Lactation; D016018:Least-Squares Analysis; D008137:Longitudinal Studies; D008433:Mathematics; D015233:Models, Statistical; D013997:Time Factors