An application of maximum likelihood and generalized estimating equations to the analysis of ordinal data from a longitudinal study with cases missing at random.

Data are analysed from a longitudinal psychiatric study in which there are no dropouts that do not occur completely at random. A marginal proportional odds model is fitted that relates the response (severity of side effects) to various covariates. Two methods of estimation are used: generalized estimating equations (GEE) and maximum likelihood (ML). Both the complete set of data and the data from only those subjects completing the study are analysed. For the completers-only data, the GEE and ML analyses produce very similar results. These results differ considerably from those obtained from the analyses of the full data set. There are also marked differences between the results obtained from the GEE and ML analysis of the full data set. The occurrence of such differences is consistent with the presence of a non-completely-random dropout process and it can be concluded in this example that both the analyses of the completers only and the GEE analysis of the full data set produce misleading conclusions about the relationships between the response and covariates.

[1]  Kanti V. Mardia,et al.  Families of Bivariate Distributions , 1970 .

[2]  J. G. Findlay,et al.  Correcting for the bias caused by drop-outs in hypertension trials. , 1988, Statistics in medicine.

[3]  L. Zhao,et al.  Correlated binary regression using a quadratic exponential model , 1990 .

[4]  S. Zeger,et al.  Longitudinal data analysis using generalized linear models , 1986 .

[5]  A Heyting,et al.  Statistical handling of drop-outs in longitudinal clinical trials. , 1992, Statistics in medicine.

[6]  S. Zeger,et al.  Multivariate Regression Analyses for Categorical Data , 1992 .

[7]  A Agresti,et al.  A survey of models for repeated ordered categorical response data. , 1989, Statistics in medicine.

[8]  N M Laird,et al.  Missing data in longitudinal studies. , 1988, Statistics in medicine.

[9]  A L Gould,et al.  A new approach to the analysis of clinical drug trials with withdrawals. , 1980, Biometrics.

[10]  D. Rubin,et al.  Statistical Analysis with Missing Data. , 1989 .

[11]  J M Neuhaus,et al.  An annotated bibliography of methods for analysing correlated categorical data. , 1992, Statistics in medicine.

[12]  M. Kenward,et al.  Alternative approaches to the analysis of binary and categorical repeated measurements. , 1992, Journal of biopharmaceutical statistics.

[13]  G G Koch,et al.  A general methodology for the analysis of experiments with repeated measurement of categorical data. , 1977, Biometrics.

[14]  P. McCullagh,et al.  Generalized Linear Models , 1984 .

[15]  R. Plackett.  A Class of Bivariate Distributions , 1965 .

[16]  J. Dale.  Global cross-ratio models for bivariate, discrete, ordered responses. , 1986, Biometrics.

[17]  G. Molenberghs,et al.  Marginal Modeling of Correlated Ordinal Data Using a Multivariate Plackett Distribution , 1994 .