In the multinomial goodness-of-fit test, it is well known that the log-likelihood ratio statistic
T has a limiting chi-square distribution under a simple null hypothesis. Siotani and Fujikoshi (1984) derived an asymptotic expansion for the null distribution of the log-likelihood ratio statistic
T under a simple null hypothesis. They proposed
J1+
Ĵ2 as an approximation of the lower probability of
T, where
J1 is a term of multivariate Edgeworth expansion and
Ĵ2 is a first order approximation of a discontinuous term. In this paper, we introduce discrete Bartlett-type transformed statistics
T* and
T** of the log-likelihood ratio statistic
T that are constructed from
J1 and
Ĵ2. By numerical comparison, we found that the accuracy of approximation of the log-likelihood ratio statistic
T to a chi-square distribution is improved by
T* or
T**.
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