sampling techniques

target population

the large group of people the researcher wishes to study

sampling frame

list of people from the target population from which the sample is drawn

sample

small group of people who represent the target population and who are studied

opportunity technique

researcher uses people who are available at that time and willing to take part

self-selected technique

researcher uses people who volunteer to participate in the study, they select themselves as participants

random technique

every member of the target population has to be available to the researcher. each person has an equal chance of being chosen.

systematic technique

involves selecting every nth number on the list of the target population

stratified technique

selecting participants in proportion to their frequency in the target population

quota technique

same process as stratified; researcher chooses (opportunity) who becomes part of the sample for each subgroup

snowball technique

current participants recruit further participants from people that they know who would be suitable for the study

opportunity strengths

easier than other sampling techniques

- approach who is available at the time and requires little planning

opportunity weaknesses

- unrepresentative: if sample is only from one place so it is hard to generalise to the target population

- researcher bias

self-selected strengths

- adverts can reach a wide variety of participants

- lack of researcher bias

self-selected weaknesses

- volunteers tend to be more motivated to participate so participants will be similar

- only people who see the advert will be able to volunteer

random strengths

- no researcher bias: P's selected randomly

- all members have equal chance of being chosen because P's are chosen from the whole target population

random weaknesses

can be time consuming - if members randomly chosen don't participate the process must be restarted

systematic strengths

- quicker than other methods as no calculations needed

- unbiased because no researcher influence

systematic weaknesses

- sample may not be representative by chance

- people selected may say no, process restarted

stratified strengths

- most representative of target population as all subgroups are represented so we can generalise the results

- no researcher bias

stratified weaknesses

- time consuming compared to other methods: if P's refuse process must be restarted

quota strengths

most representative of target population as all subgroups are represented so we can generalise the results

quota weaknesses

- researcher bias because P's are chosen using opportunity sampling

- time consuming because calculations are needed

snowball strengths

enables the researcher to locate groups that may be difficult to access

snowball weaknesses

not representative because recruits will chose people that are similar to them