The relationship between double‐exponential families and extended quasi‐likelihood families, with application to modelling Geissler's human sex ratio data

The human sex ratio data, collected in Saxony in the 19th century by Geissler, are reanalysed by joint modelling of the mean and dispersion. Extended quasi-likelihood and the unnormalized double-exponential family are shown to lead to identical inference. The use of the unnormalized form is discussed. The relationship between multinomial and Poisson models is studied for overdispersed data.