A sample is a smaller group selected from the general populations chosen to take part in research. Sampling is the process of finding a sample to participate in research. Many researchers use Sampling Frames to help them identify a relevant sample; this is a list of potential participants. Examples of this are: electoral register, postcode address file, telephone directory, school attendance registers and GP patient records.
Random sampling and in principle ensures everyone has an equal chance of being selected. This doesn't ensure that the information is a representative sample. There are 3 variations of random sampling frames:
Systematic- Randomly choosing a number between one and ten (7) and then picking out every tenth number after that (7, 17,27,47 etc) until the sample is complete.