[Negative binomial distribution of eggs of Schistosoma japonicum in stool]

To understand the nature of distribution of schistosoma japonicum (S. japonicum) eggs in stool of the infected individuals, it is assumed that if regression coefficient b approaches two in the equation lg (v) = a + blg(m), with a larger mean of egg counts (m), they can be considered compatible with negative binomial distribution. Results of this study showed egg counts of S. japonicum in stool of the same infected individual on different days and in male and female population can be described by negative binomial distribution, with 95 percent confidence intervals of coefficient of regression 1.3006-2.2956, 1.6109-1.9703, 1.7060-2.1589, and 1.5507-2.2359, respectively. Goodness of fit tests for the observed data indicated that fitting for negative binomial distribution was good. It suggests that the method of moments (coefficient of regression) can be used to determine whether the observed distribution of frequencies is compatible with a negative binomial one.