Lesson 04 - sampling methods

define random sample

every member of the target population has an equal chance of being selected

define systematic sample

every nth person is chosen from a list

define stratified sample

the proportions of people in population subgroups (strata) are reflected in the sample

define opportunity sample

whoever is available at the time of sampling will be included 

define volunteer sample

participants self select

evaluate volunteering

a particular type of person offers to take part in research; thus, the sample is likely to be biased (and can’t be generalised to the rest of the population - low ecological validity)

evaluate opportunity

high chance the sample will be biased (and can’t be generalised to the rest of the population - low ecological validity)

evaluate systematic

this is a very objective method, especially if the researcher does not pick the criteria for sampling. but people picked may refuse to take part, so the sample becomes unrepresentative

evaluate stratified

the sample is likely to be representative so can be generalised to the target population. but it is difficult and time consuming to get full details of the subgroups within the target population. people picked may be unwilling to take part

evaluate random

the sample is likely to be representative so it can be generalised to the target population. it is unbiased. need to obtain a full list of the population, people picked may be unwilling to take part