SAMPLING

• Sampling involves selecting participants from a target population.
• The target population is the particular subgroup to be studied, and to which the research findings will be generalised.
• A target population is usually too large to study in its entirety, so sampling techniques are used to choose a representative sample.
• Random sampling involves identifying everyone in the target population and then selecting the number of participants you need in a way which gives everyone an equal chance of being selected, such as pulling names from a hat, or using a computer software package which generates names/numbers randomly and without bias.
• Systematic sampling involves using a predetermined system to select participants.
• Stratified sampling involves identifying subgroups within a population and obtaining participants from each stratum in proportion to their occurrence within the population.
• There are issues of bias, however, with an opportunity sample.
• There are limitations associated with the stratified sampling method.
• The first 20 volunteers would form part of their sample.
• Opportunity sampling consists of selecting anyone who is available and willing to take part in the study at the time.
• Those individuals who are more curious or inquisitive by nature may volunteer more readily.
• A strength of volunteer sampling is that participants generally approach the researcher rather than the other way around.
• In comparison to all other sampling methods, obtaining an opportunity sample is quicker and easier since it requires less effort on behalf of the researcher.
• The sample is likely to be biased and not representative of the target population, which makes generalisation of the findings more difficult.
• A truly representative sample would be extremely difficult to obtain using this technique.
• There are issues of bias associated with volunteer sampling.
• A psychologist could place posters in various locations around a school asking for A-level students to volunteer to take part in their study, providing an email address to reply to or a time, date and venue to attend for participation.
• This significantly reduces the possibility of the researcher choosing a biased sample of participants who would serve to support their aims.
• As a result, this makes obtaining a sample quicker and easier, in comparison to other methods.
• Any findings generated from research with a stratified sample can be generalised to the target population with greater confidence.
• Ensuring that the subgroups/strata in the target population are all accurately identified is sometimes a difficult and time-consuming task.
• A strength of obtaining a stratified sample is that it is largely free from researcher bias.
• In this technique, the sample is generated randomly once the subcategories/strata have been identified.
• This is a technique which is often used in psychological research due to its ease of application.
• Volunteer sampling consists of participants self-selecting to take part in a study by either volunteering when asked or by responding to an advert.
• Very often it is a particular type of person that is likely to take part in research as only those who see the advert will come forward to participate.
• This means that the technique requires minimal effort and input on behalf of the researcher.
• As the sample is drawn from a very specific area or location, e.g university, this means that it is likely only students will be available to take part who are not representative of the target population.
• Furthermore, stratification is not a perfect process since the subgroups identified cannot possibly reflect all the individual differences that exist between those in the target population.
• A strength of opportunity sampling is the convenient nature of the technique.
• A stratified sample is likely to be representative because each particular subgroup, if selected appropriately, will be represented within the sample.
• There is an increased risk of investigator bias as the researcher has complete control over who they approach.