Statistical Analysis of Female Proportion among the Japanese Infant Population of 0-4 Year Olds

Abstract

We deal with the problem of whether or not there is an increase in female proportion among 0-4 year olds in the Japanese population during the last 21 years. The validity of the use of a binomial model for analyzing the municipality-specific data of female proportion is examined using a beta-binomial model. It is suggested from a logistic regression analysis that there exists a difference of the female proportion of infant population among population-size-specific groups of municipalities. The highest proportion was observed for the rural group, and the lowest one was observed for the city group. A slight but statistically signifant increasing time-trend in female proportion among the city group is detected via a test with the null hypothesis that the proportions of females are all equal against an ordered alternative.