PARAMETERS OF DISPERSION FOR ON-TIME PERFORMANCE OF POSTAL ITEMS WITHIN TRANSIT TIMES MEASUREMENT SYSTEM FOR POSTAL SERVICES

Abstract

The paper is focused on usage of methods for on-time performance evaluation of test postal items flows used for measurement of the transit time of end-to-end postal services for single piece priority mail. The results come out from modelling of measurement system for postal transport network efficiency in proportion to real postal traffic flows with particular discriminant characteristics. The result of on-time performance is represented by estimate of on-time probability, which can be defined as probability of case, when transit time of postal item does not exceed just one day. On-time probability is interpreted by variable called weighted estimate of on-time probability, which also includes distribution of mail flows within geographical stratification according to disjunctive set of defined postal areas. The rate of variability caused by used sample design is expressed by parameters of sample dispersion in various forms and by design factors regarding particular samples. Assessment of these calculated key parameters is the main objective of this paper, because they evaluate measurement system efficiency and could serve as base for next modelling of this system. Calculation of these parameters presumes fixed postal transportation network and domestic mail flows for various sample sizes.