Every piece of research requires a sample, and there are many ways of finding a suitable sample. Before choosing a method the researcher must find a ‘sampling frame’, this is the collection of people the researcher will then choose their sample from. An example of this could be school or college.
Random sampling – an example of random sampling would be picking names out of a hat. In random sampling everyone in the population has the same chance of getting chosen. This is easy because it is quick and can even be performed by a computer. However, because it is down to chance you could end up with a unrepresentative sample, perhaps with one demographic being missed out.
Systematic sampling – an example of a systematic sample would be picking every 10th person on a list or register. This carries the same risk of being unrepresentative as random sampling as, for example, every 10th person could be a girl.
Stratified sampling – this method attempts to make the sample as representative as possible, avoiding the problems that could be caused by using a completely random sample. To do this the sample frame will be divided into a number of smaller groups, such as social class, age, gender, ethnicity etc. Individuals are then drawn at random from these groups. If you are observing doctors and you had split the sample frame into ethnic groups you would draw 8% of the participants from the Asian group, as you know that 8% of doctors in Britain are Asian.
Quota sampling – In this method researchers will be told to ensure the sample fits with certain quotas, for example they might be told to find 90 participants, with 30 of them being unemployed. The researcher might then find these 30 by going to a job centre. The problem of representativeness is again a problem with the quota sampling method.
Cluster sampling – This is taking a random sample at various stages of the sampling process. For example you might take a random county, take random schools from this county and take random pupils from this school to find your sample.
Snowball sampling – With this method, researchers might find a few participants, and then ask them to find participants themselves and so on. This is useful when a sample is difficult to obtain. For example Laurie Taylor used this method when investigating criminals. It would be difficult for him to find a sample as he didn’t know many criminals; however these criminals know a lot of people who would be willing to participate, so it is more efficient to use the snowball method.