L4 sampling main.

Methodology: Sampling methods.

LO: To understand the different types of sampling methods and

the strengths and weaknesses of these methods.

Key Words Key Words ActivityActivity

1. Closed questions1. Closed questions

2. Questionnaires2. Questionnaires

3. Variables3. Variables

4.Representative4.Representative

5. Sampling5. Sampling

6. 6. Sampling FrameSampling Frame

Starter: Write down as many of the key words that you can remember

from the presentation (6).

Match each key word with the definition.

• Can be answered with a limited choice of answers from a pre-set list

• A method for collecting information and drawing inferences about a larger population or universe

• Consisting of a series of questions and other prompts for the purpose of gathering information from respondents

• a list that includes every member of the population from which a sample is to be taken

• a typical example or specimen of a group, quality, or kind

• Any factor that can change or vary

• Closed questions- Can be answered with a limited choice of answers from a pre-set list

• Sampling- A method for collecting information and drawing inferences about a larger population or universe

• Questionnaire- Consisting of a series of questions and other prompts for the purpose of gathering information from respondents

• Sampling Frame- a list that includes every member of the population from which a sample is to be taken

• Representative- a typical example or specimen of a group, quality, or kind

• Variable- Any factor that can change or vary

Population: the whole group your are studying. E.g. Year group or school.

Sampling Frame: A list of names from the population. E.g. electoral register, school registers, phone books.

Sample: those taking part in the research. This sample is usually drawn from the sampling frame.

How do you choose people to research?

• Sampling is how you choose individuals to research.

• There are 6 different types of sampling.

1. Random Sample

• Random Samples give every member of the sampling frame an equal chance of being selected.

• Every name is given a number and then a list of random numbers is used to select the sample.

What could be the strengths and weaknesses of this method?

Strengths Weaknesses

•Avoids bias/ subjective judgements of who to include. •Everyone has equal chances of being selected.

•Not a representative sampling type, people with certain variables could get left out, i.e. accidentally you could choose all men- Implications for your findings?

2. Systematic sample• Every 3rd person stand up. • This form of sampling selects people from

the sampling frame by choosing every nth person.

• For example, if you were researching a business you may take every nth number person on their employee list.

What could be the strengths and weaknesses of this method?

• Similar to random sampling.

3. Quota Sampling• Is used commonly by market researchers

in town centres. • The researcher has quotas to fill, i.e. you

might need 25 women under 35. So the researcher will ask the first 25 women who meet these requirements to include in the research. This will continue until all the quotas are filled.

• What are the strengths and weaknesses of this method of sampling?

Strengths and weaknesses of quota sampling

Strengths Weaknesses1. Bias, the people are

selected on appearance, so people may be excluded.

2. The sample will differ depending on the time of day and place in which it is conducted, e.g. if conducted mid day in town many of the sample may be unemployed.

3. Consequently, not representative.

1. Simple, quick and easy.

2. You can get people with the desired characteristics e.g. gender, ethnicity, age.

4. Stratified Sampling4. Stratified Sampling

• This sampling method involves the research population being divided into different strata in terms of the populations variables, i.e. gender, age, ethnicity.

• A sample is then drawn which include people with these characteristics.

• Each strata needs to be representative of the general population

4. Stratified Sampling

• So, your target is Year 10 Psychology Students……

• In the year, there are 50 male psychology students, and 150 female….

• You need 20 participants, how many males and females should you use?

The sampling frame is divided into ‘strata’. A random sample is then taken from each stratum

4. Strengths and weaknesses of stratified sampling

Strength Weakness

1. Can only use this form of sampling if you have the required information to draw the sample, which can be difficult to obtain. E.G Electoral registers can be used as a sampling frame, yet if you wished to study religion they would be of no use.

1. Provide a representative sample, as the sample is selected on the basis of the required variables.

5. Snowball sampling• This sampling method involves using a

network of like minded or like situated individuals.

• By accessing one person suitable for your study, you can then, via them find other people for your study.

• Very good for sensitive subjects, such as people who have been subject to domestic violence and go to a support group or hard to access groups such as gypsies or sensitive communities.

What are the advantages and disadvantages of snowball sampling?

Strengths Weaknesses

1. Can access people who are difficult to access. i.e. if there is no present information for a sampling frame, or if the group is so small that normal sampling methods would not access them.

2. Can access groups of like minded people who do not wish to be identified i.e. drug users.

1. The sample will not be representative as it relies on personal recommendation.

2. Will not be able to make generalisations as sample is not representative.

6. Volunteer Sampling• Another sampling method to use when it is

difficult to find a sampling frame. • Advertisements will announce the

research and request volunteers for the sample.

• Same advantages and disadvantages of snowball sampling.

• Further disadvantage: Subjects are self selected.

7. Convenience/Opportunity Sample

• Finding participants who are easily accessible– e.g. in the street

• Advantage– cheap and easy– Takes less time to locate sample

• Disadvantage– Biased because the sample is drawn from a small part of the

target population