should resort to random sampling so that bias can be eliminated and sampling error can be estimated.
But purposive sampling is considered desirable when the universe happens to be small and a known
characteristic of it is to be studied intensively. Also, there are conditions under which sample designs
other than random sampling may be considered better for reasons like convenience and low costs.
The sample design to be used must be decided by the researcher taking into consideration the
nature of the inquiry and other related factors.