The result in this article shed some new light on UMVUEs in presence of ancillaries.
Our approach also generated the open problems of proving or disproving completeness of (2.9)-2.11).
It may be note that each of these three distribution families is a scale as well as a curved exponential family.
Since Fisher (1925,1934) introduced ancillary statistics,
their role in statistical inference has been discussed by many researchers, e.g., Basu (1964), Cox (1958,1971), Fraser (2004) and Ghosh et al. (2010).
A general them is that one should condition on an ancillary statistic for making inferences,
but the choice of the ancillary may be difficult and controversial, see Basu (1964).
However, our Example 2 provides another reason for conditioning on the sample size if it is ancillary.