sampling Flashcards
random sample
Every member of the target population has an equal chance of being selected.
lottery method
strenght of random sample
unbiased, conf extr variables equally divided between groups, internal val.
3 limitations random sample
difficult and time consuming, a complete list of target population difficult to obtain.
may end up with unrepresentative sample, 20 females.
selected ppts may refuse to take part, end up with more volunteer sample.
systematic sample
every nth member of the target population is selected. sampling frame produced ( in age order), sampling system nominated , may begin randomly start.
strength systematic sample
objective, once system established no influence over who is chosen.
limitation systematic sample
time-consuming and ppts may refuse to take part.
stratified sample
The proportions of people in population subgroups (strata) are reflected in the sample.
strength stratified sample
representative sample, designed to accurately reflect the composition of the population, generalisation high.
limitation stratified sample
identified strata cannot relfect all the ways that people are different, complete representation is not possible.
opportunity sample
Whoever is available at the time of sampling will be included.
strengths opportunity sample
convenient, less costly, list of all members not needed.
limitation opportunity s
unrepresentative target population, drawn from specific area, cant gen
researcher complete control over selection of ppts, may avoid certain ppts, researcher bias.
volunteer sample
Participants ‘self-select’.
strength volunteer s
minimal effort from researcher, less- consuming of time, more engaged ppts
