Comparison of two approximation methods to deal with PPP phenomenon in practice

During the combination and fitting of derived quantities, one must pay attention to so called PPP phenomenon. Chiba and Smith proposed an approximation method to be used in practices. Which is equivalent to the approximation suggested by Zhou. The author, present an approximation. The comparison of these two approximations is carried out for several examples. It has been found that two approximations give better estimates and that the author's approximation seems better in the case of increment deriving function while Chiba's better for decrement deriving function. (1 fig.)