Revision as of 20:47, 7 November 2009

Data are called provisional ¹ if they are based on incomplete or insufficiently controlled observations. They are replaced by final ² data when the observations are complete. Rates based on such data are called provisional rates ³ and final rates ⁴ respectively. Where information becomes available after figures have already been published, revised rates ⁵ may be issued. The expression corrected rate ⁶ usually implies that defective data or inappropriate methods have yielded results which are either misleading or of limited value for the purpose in hand and that an effort has been made to correct this, e.g., correction for underenumeration, correction for migration, correction for seasonal movement. Standardized rates ⁷ or adjusted rates ⁷ are designed to make it possible to compare different populations with respect to a variable, e.g. fertility or mortality, where the influence of another variable e.g. age, is held constant. The term corrected rate ⁷ has been used by some demographers as a synonym for standardized rate. When the data do not permit direct estimation of the rates (small population, for example), the use of standard rates ^9★ (cf. 403-6 for example) computed from data of good quality and applied to the real population, provides an indirect estimation of the expected number of events which can be compared with the observed number of events. Unstandardized rates are called crude rates ⁸. Although they may be used to measure actual trends, false inferences may result from their uncritical use when populations with different structures (144-4) are compared. More...