General Logistic Model Research Articles

A Simple, Stable Model of Mutualism Incorporating Handling Time

Description d'un modele simple de mutualisme faisant intervenir 2 especes, qui prend en compte le temps de «manipulation» d'une ressource alimentaire (depuis sa rencontre jusqu'au debit de la recherche de nouvelles ressources)

Forecasting with growth curves: the effect of error structure.

"The main theme of this paper is an investigation into the importance of error structure as a determinant of the forecasting accuracy of the logistic model. The relationship between the variance of the disturbance term and forecasting accuracy is examined empirically. A general local logistic model is developed as a vehicle to be used in this investigation. Some brief comments are made on the assumptions about error structure, implicit or explicit, in the literature." The results suggest that "the variance of the disturbance term, when using the logistic to forecast human populations, is proportional to at least the square of population size."

The Relation between Score Tests and Approximate UMPU Tests in Exponential Models Common in Biometry

In several recent papers, both published and unpublished, the theory of score tests (Rao, 1973, pp. 415-420), or the equivalent C(a) test (Neyman, 1959), has been used to derive tests involving likelihoods based on exponential families which yield sufficient statistics. A recently published example is a paper by Day and Byar (1979) in which the test for combined 2 x 2 tables due to Cochran (1954) [sometimes called the Mantel-Haenszel (1959) statistic] is shown to be a 'logit score test'. Day and Byar also considered a second multiparameter test for a more general logistic model. We shall show that, in such cases, score tests can ordinarily be written down directly upon examination of the structure of the likelihood; neither differentiation of the likelihood nor matrix inversion is usually needed. Furthermore, for the case in which a single parameter is tested in the presence of nuisance parameters, the score test is simply the normal approximation to the uniformly most powerful unbiased (UMPU) test. Obviously, for one-parameter exponential families the score test is not only asymptotically locally most powerful but is also an approximation to the UMPU test (Efron, 1975).

The effect of nonzero second-order interaction on combined estimators of the odds ratio

SUMMARY In combining odds ratios across strata, the assumption of zero second-order interaction is usually made in order to simplify estimation. The implications for the use of the general logistic model, when this assumption is not met, are considered. Using Monte Carlo techniques, the effect of nonzero second-order interaction on five available combined estimators is considered and an attempt made to provide results applicable in a variety of research situations.