sampling

• A representative sample is a sample that reflects the original population
• volunteer sampling is when a researcher posts an advert and people volunteer to be participants in the study.
• A strength of volunteer sampling is that it is easy, and can reach lots of people. However, volunteers will often not be representative of the general population.
• opportunity sampling is when a researcher approaches members of the population who are willing and available to be participants.
• A strength of opportunity sampling is that it is quick and easy to obtain a sample. However, participants will often not be representative of the general population
• systematic sampling which is when researchers pick every nth person from the entire population
• A strength of systematic sampling is that it will often lead to a more representative sample than volunteer or opportunity sampling because it involves sampling from the whole population. However, it is difficult as the researcher has to obtain a list of the whole population. Also, if there is a pattern in how the data is listed, the sample may not be representative of the population
• Random sampling involves picking randomly from a list of the entire population, so that everyone has an equal chance of being a participant
• A strength of random sampling is that it is representative because every member of the population has an equal chance of being included. However, it is a more difficult method of sampling because you need a list and a way to randomise it. Also, it doesn't guarantee a representative sample
• Stratified sampling involves researchers ensuring that their sample has the same proportion of each subgroup as the total population.
• To obtain a stratified sample, researchers must identify important subgroups within the target population and then identify how many people from each subgroup are needed to have the same proportion as the original population. Researchers must then sample randomly from each subgroup until they get the required number of participants
• A strength of stratified sampling is that it is very representative of the target population and it is the best method to ensure the sample resembles population ensuring high population validity. However, researchers may miss out an important subgroup by mistake making the sample not completely representative. It is also difficult and time-consuming.