Because variables conforming only to nominal or ordinal measurements cannot be reasonably measured numerically, sometimes they are grouped together as categorical variables , whereas ratio and interval measurements are grouped together as quantitative variables , which can be either discrete or continuous , due to their numerical nature. Such distinctions can often be loosely correlated with data type in computer science, in that dichotomous categorical variables may be represented with the Boolean data type , polytomous categorical variables with arbitrarily assigned integers in the integral data type , and continuous variables with the real data type involving floating point computation. But the mapping of computer science data types to statistical data types depends on which categorization of the latter is being implemented.
The index numbers of the costs of labour presented in this report are compiled based on data contained in GF527 returns provided to the Census and Statistics Department (C&SD) by various government works departments. GF527 is an administrative return for reporting site labour deployment and wage rates for construction works by main contractors of public sector construction projects. According to the instructions issued by the Development Bureau, contractors should be responsible for the accuracy of the data entered while site supervisory staff of the works departments concerned should check and sign the returns submitted by contractors before delivering the returns to C&SD via their project offices. C&SD's role in the exercise is to consolidate the data received to compute and disseminate statistics on average daily wages for 33 selected occupations and based on which, the index numbers of the costs of labour used in public sector construction projects.