ABSTRACT
In the previous chapters, we had assumed implicitly that the basic data collected either through a complete enumeration or a sample are free from any error or bias and that the (unbiased) estimates obtained from a sample are subject only to sampling errors. This is not so in actual survey conditions. From the stage of collection to that of preparation of final tables, the data are generally subject to different types of errors and biases. In this chapter will be reviewed the various types of errors and biases in data and in estimates derived from them and the methods of measurement and control of these errors and biases.
