****REMINDER - THIS WEDNESDAY****
Ordinary meeting of the Royal Statistical Society organized by the
Research Section
Wednesday, April 18th, 2007 at 5pm (tea from 4:30pm)
Venue: Royal Statistical Society, 12 Errol St, London EC1Y 8LX
P. Diggle (Lancaster University), D. Farewell (Cardiff University) and
R. Henderson (University of Newcastle)
Analysis of longitudinal data with drop-out: objectives, assumptions
and a proposal
The problem of analysing longitudinal data that are complicated by
possibly informative drop-out has received considerable attention in
the statistical literature. Most researchers have concentrated on
either methodology or application, but we begin this paper by arguing
that more attention could be given to study objectives and to the
relevant targets for inference. Next we summarize a variety of
approaches that have been suggested for dealing with drop-out. A
long-standing concern in this subject area is that all methods require
untestable assumptions. We discuss circumstances in which we are
willing to make such assumptions and we propose a new and
computationally efficient modelling and analysis procedure for these
situations. We assume a dynamic linear model for the expected
increments of a constructed variable, under which subject-specific
random effects follow a martingale process in the absence of drop-out.
Informal diagnostic procedures to assess the tenability of the
assumption are proposed. The paper is completed by simulations and a
comparison of our method and several alternatives in the analysis of
data from a trial into the treatment of schizophrenia, in which
approximately 50% of recruited subjects dropped out before the final
scheduled measurement time.
You can download/view a PDF copy of this paper at
http://www.rss.org.uk/main.asp?page=1836#1120
Trevor Sweeting
Chair, RSS Research Section Committee
|