Random sampling- definition
Each person has an equal chance of being picked. Every member of the target population has to be available to the researcher. E.g the use of a random name/ number generator or pick out the hat
Random sampling- strengths
Fairest way to select a sample
Easy to do as it uses random number generator or names in a hat
Random sampling- weaknesses
Not necessarily the most representative way of selecting a sample
Opportunity sampling- definition
Researcher uses people who are available at that time because it is easy inconvenient, for example using students that are on free period in the canteen
Opportunity sampling- strengths
Easier and more convenient way of selecting participants compared to other techniques like random sampling
Opportunity sampling- weaknesses
People available may not be representative of the target population. Not everyone has an equal chance of taken part and therefore it is unfair.
Systematic sampling- definition
A whole list of the sampling frame is needed to select participants, for example tutor group registers in college, names are systematically taken from each register for example every 10th name
Systematic sampling- strengths
The sample tends to be more representative than opportunity sampling. The method avoids research of bias as it uses a system.
Systematic sampling- weaknesses
It is not the fairest way to select a sample as not everyone has an equal chance of being chosen. It’s not as representative as quota or stratified sampling.
Stratified sampling- definition
The sample is divided into groups that the researcher wants to make sure are representative in the final sample, for example 20 students are selected to attend an A-level psychology conference, the teacher then randomly sets 12 girls and eight boys from the sampling frame.
Stratified sampling- strengths
It guarantees a representative sample of the target population by using ratios. It is a far way of selective participants.
Stratified sampling- weaknesses
It’s time consuming because participants need to be assessed and categorise before a sample can be drawn from the population.
Quota sampling- definition
When a quote of participants are needed to provide a representative sample, for example, opportunity of volunteer
Quota- strengths
Representative of the sampling frame and maybe quicker than stratified sampling
Quota- weaknesses
Not as spare as stratified sampling as only the participants available at the time of the study have a chance to take part and it is time-consuming
Self-selected sampling- definition
Researcher uses people who take w they volunteer when asked or have responded to an advert.
Self-selected sampling- strengths
Research is gain willing participants who want to take part in the study compared to samples like random where participants may refuse.
Self-selected sampling- weaknesses
Can be highly unrepresentative as a certain type of people are likely to participate in the study
Snowball sampling- definition
Can be used if your population is not easy to contact for example if you were interested in studying students who take legal drugs you may ask participants with desired characteristics to give names of further appropriate participants or tell Friendto tell Friend to tell Friend
Snowball sampling- strengths
Enable the research to locate groups of participant to are difficult to access 
Snowball sampling- weaknesses
Unlikely to be representative of the target population as friends of friends and no equal chance of being selected
