ABSTRACT
There are several basic methods used to collect primary data; these are the main ones: asking questions, conducting interviews, observing without getting involved, immersing oneself in a situation, doing experiments, and manipulating models. Different disciplines use one or several of these methods to collect data, and customize them to cater for their needs. If the data researcher's collect really are the same as they would get from the rest, then researchers can draw conclusions from those answers which they can relate to the whole group. This process of selecting just a small group of cases from out of a large group is called sampling. There are basically two types of sampling procedure: probability sampling, and non-probability sampling. In order to be able to generalize the results beyond the confines of the experiment itself, the experiment should really reflect the situation in the real world – it should possess both internal validity and external validity.
