sampling techniques Flashcards
sampling techniques definition
the method used to select people from the population
sample definition
a group of people who take part in a research investigation. The sample is drawn from a target population and is presumed to be representative of that population
population definition
a group of people that are the focus of the researcher’s interest, from which a smaller sample is drawn
volunteer sample
involves participants selecting themselves to be part of the sample
volunteer sample strengths
- collecting it is easy as it requires minimal input from the researcher so less time consuming
- researcher ends up with more engaged participants
volunteer sample weaknesses
- volunteer bias is a problem as asking for volunteers may attract a certain profile of person (one that is more curious and likely to please the researcher which affects generalisation)
opportunity sample
researchers select anyone who happens to be willing and available
opportunity sample strengths
- convenient
- less time consuming
- more economical
- list of target population is not required so there is no need to divide the population
opportunity sample weaknesses
- has 2 forms of bias
- sample is unrepresentative of the target population as it is drawn from a specific area so findings cannot be generalised to the target population
- the researcher has control over the selection of participants so may avoid some people
random sample
sophisticated form of sampling in which all members of the target population have an equal chance of being selected
random sample strengths
- potentially unbiased as EVs and CVs are equally divided between different groups
random sample weaknesses
- difficult and time-consuming to conduct as a complete list of target population may be difficult to obtain
- may end up with a sample that is still unrepresentative
- selected participants may refuse to take part
stratified sample
sophisticated form of sampling in which the composition of the sample reflects the proportions of people in certain subgroups within the target population
how to carry out a stratified sample
- identify the strata (subgroups) in the target population
- calculate the proportions of the target population that each strata represents
- select the calculated number of people needed from each strata randomly so the sample represents the population
stratified sample strengths
- produces a representative sample because it is designed to accurately reflect the composition of the population so generalisation of findings is possible
stratified sample weaknesses
- identified strata cannot reflect all the ways that people are different, so complete representation of target population is not possible
systematic sample
when every nth member of the target population is selected
systematic sample strengths
- avoids bias because member selection happens through the use of a sampling interval (as long as interval and starting place is chosen randomly)
- objective because once the system for selection is established, researcher has no influence over who is chosen
systematic sample weaknesses
- time consuming
- participants may refuse to take part
- sample is not representative as every nth member may be a male for example
bias
when certain groups are over or under represented within the sample selected. This limits the extent to which the generalisations can be made to the target population
generalisation
the extent to which findings and conclusions from a particular investigation can be broadly applied to the population. This is possible if the sample of participants is representative of the target populaton
how to conduct a random sample
- researcher obtains list of names of target population
- allocate them all a different number
- use a random number generator to randomly select 20 numbers
- numbers converted back to names and these are the 20 participants
