Sampling

• the population refers to the group of individuals that a particular researcher may be interested in studying. this is often called the target population because is it a subset if the general population. a researcher will select a sample group known as the sample. the sample must be representative of the target population so that generalisation of findings are possible. samples are selected using a sampling technique that produces a non bias sample
• a random sample is when all members of the target population have an equal chance of being selected. to select a random sample, the researcher must create a list of all members in the target population. then all the names are assigned a number. the sample is generated through some use of lottery method
• one strength of a random sample is that they are free from researcher bias. this is because the researcher has no influence on who is selected and this prevents them from choosing people who they think may support their hypothesis
• a limitation of sampling is that they are difficult and time consuming to conduct. this is because a complete list of the target population is extremely difficult to obtain. also, the sample may be unrepresentative as the random sample may choose people with all the same characteristic.
• a systematic sample is when every nth member of the target population is selected. a sampling frame is produced which is a list of people in the target population which is organised. a sampling system is nominated (every 3rd 6th person etc) or this interval may be determined randomly to avoid bias. the researcher then works through the sampling frame until the sample is complete
• one strength of the systematic sample is that is avoids researcher bias. this is because once the system for selection has been established, the researcher has no influence over who is chose. it is also representative
• a stratified sample is a form of sampling in which the composition of the target sample reflects the proportion of people in certain sub groups knows as strata within the target or wider population. the researcher must identify the different strata that make up a population. then the proportions needed for the sample to be representative are worked out. the participants that make up each stratum are then selected using random sampling
• one strength of stratified sampling is that it avoids researcher bias. once the target population has been sub divided into strata, the participants that make up the numbers are randomly selected and beyond the influence of the researcher. also, stratified samples are representative because it is designed to accurately reflect the composition of the population meaning generalisations can be made
• a limitation of stratified samples is that stratification is not perfect as the identified strata cannot reflect all the ways that people are different so complete representation of the target population is not possible
• the researcher may choose an opportunity sample to select anyone who is willing and available. the researcher takes the chance to ask whoever is around at the time of their study
• one strength of opportunity samples is that they are convenient. this method saves a researcher a lot of time and effort and is much less costly in terms of time and money.
• a limitation of opportunity sampling is that they suffer from bias. firstly, the sample is unrepresentative of the target population as it is drawn from a very specific area so findings cannot be generalised to the target population. also, the researcher has complete control over the selection of participants and may avoid certain groups which is a type of researcher bias
• a volunteer sample involves participants selecting themselves to be part of the sample. to select a volunteer sample a researcher may place an advert in a newspaper etc or willing participants may simply raise their hand when the researcher asks
• one strength of volunteer samples is that it is easy. it requires minimal input from the researcher and is less time consuming that other forms of sampling
• a limitation of volunteer sampling is volunteer bias. asking for volunteers may attract a certain profile of person which means results cannot be generalised