1. Types of data

　　2. Secondary data

　　3. Sampling methods

　　2.1 Types of data

　　Data can be classified as follows:

　　(a)Primary and secondary data

　　Primary data – are data collected especially for a specific purpose.

　　Secondary data – are data which have been collected elsewhere, for some

　　other purposes, but which can be used or adapted for the

　　survey being conducted.

　　(b)Discrete and continuous data

　　Discrete data – are data which can only be taken on a finite or countable

　　number of values within a given range.

　　Continuous data – are data which can take on any value.

　　(c )Sample and population data

　　Sample data – are data arising as a result of investigating a sample

　　Population data – are data arising as a result of investigating the population.