On the Treatment of Grouped Observations in Life Studies.
Interim technical rept.,
MISSOURI UNIV COLUMBIA DEPT OF STATISTICS
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Cox Regression models and life tables, J. Roy. Statist. Soc. 34B, 1972 presents a systematic study of the use of covariates in the analysis of life time. Coxs basic model is that of proportional failure rates. A particularly thorny point in theory and application is the treatment of tied observations. It appears that grouping rather than discrete time is the proper way to handle ties. This paper studies what to do with grouped observations. Maximum likelihood leads to ignoring intervals in which no failures occur. A logistic model, which makes explicit use of Coxs earlier binary data methods, is introduced and illustrated with a numerical example. When the grouping becomes fine this logistic model leads back to the proportional failure rate model suggested by Cox. Author
- Statistics and Probability
- Manufacturing and Industrial Engineering and Control of Production Systems