It is important for the investigator to decide whether to use sample or census method for collecting data. The selection primarily depends upon the nature and extent of the enquiry and the degree of accuracy desired.
Statistical data as we have seen can be either primary or secondary. Primary data are those which are collected for the first time and so are in crude form. But secondary data are those which have already been collected.
Philately is the pastime of collecting postage stamps. It is a hobby that originated within a few years of the first issue of penny postage in England in 1810. When and how the hobby started is not exactly known.