Sampling techniques

Question 1

Snowball sampling

Answer 1

A small number of people are invited and asked to invite other people they know to join the study.
It is used to obtain samples of participants that may be difficult to reach e.g. drug users
STRENGTH: It is cost-effective as it relies on participant referrals.
WEAKNESS: This may create a biased sample. They may not be representative of the target population so generalisability is difficult. It is also affected by researcher bias as they invite the participants first.

Question 2

Purposive sampling

Answer 2

The main characteristics of the participants are defined in advance of the study and researchers recruit participants who fit the characteristics.
STRENGTH: it may give a more representative sample of the target population
WEAKNESS: affected by researcher bias since the researchers are picking them

Question 3

Convenience/opportunity sampling

Answer 3

Consists of taking the sample from people who are available at the time & place of the study.
STRENGTH: convenient and quick for the researcher as participants are already in the area of the study and it is more cost-effective since no time is wasted looking for participants.
WEAKNESS: participants may all be a group of common people (e.g. social class) so there is very little difference in participant variability, therefore making it an unrepresentative sample of the target population. It is also affected by researcher bias as they get to pick their participants.

Question 4

Volunteer sampling

Answer 4

Participants volunteer to join the study and the study could have been advertised in posters/media etc.
STRENGTH: an easy way to obtain participants. Participants also willingly volunteered, so they may be more motivated and cooperative. There are no ethical issues as no pressure is being put on people to participate. It is also cost-effective as researchers don’t spend time looking for participants.
WEAKNESS: people who volunteered may be vastly different from people who didn’t volunteer, so the sample is not representative of the target population.

Question 5

Stratified sampling

Answer 5

Make a sample that reflects the subgroups within a target population. Classifying the target population into categories and then choosing a sample which consists of participants from each category in the same proportions. E.g. in the school we have 50% Chinese, 20% Korean, and 30% Japanese. My sample should have 20 Chinese students, 12 Japanese students and 8 Korean students.
STRENGTH: as all participants’ variables are taken into account it is much more likely to be a representative sample of the target population
WEAKNESS: it is difficult to identify the subgroups in the target population so it is time-consuming and costly

Question 6

Random sampling

Answer 6

Every member of the target population has an equal chance of being chosen (Pulling the names from a hat)
STRENGTHS: avoids researcher bias as they do not control who is chosen as a sample. It is more ethical as everyone has an equal chance of being selected.
WEAKNESS: it is time-consuming as you first have to identify the target population and then have to use a generator to pick randomly