© 1995 by Biometrika Trust
MISCELLANEA |
Second order asymptotics for score tests in generalised linear models
Department of Economics, Southern Illinois University Carbondale, Illinois 62901-4515, U.S.A.
Departamento de Estatistica, Universidade de São Paulo Caixa Postal 20570, São Paulo/SP, 01452-990, Brazil
This paper develops finite-sample corrections for score tests in generalised linear models when the dispersion parameter is unknown, thus generalising the results of Cordeiro, Ferrari & Paula (1993). We show that the coefficients which define the Edgeworth expansion for the null distribution of the score statistic when the dispersion parameter is unknown are the coefficients obtained by these authors plus some extra terms. We also give closed-form expressions for such coefficients. An important special case of our results is the normal linear regression model. Simulation results for this model show that the corrections can be very effective, reducing the probability of conflict with other asymptotically equivalent testing criteria.
Key Words: Asymptotic expansion Bartlett-type correction Chi-squared distribution Generalised linear model Score test Size-correction