Random sampling avoids bias and gives everyone an equal chance of being selected, but it may not result in a truly representative sample if certain variables are left out. Quota sampling is quick but biased based on appearance. Stratified sampling provides a representative sample by selecting participants based on variables, but requires detailed population information. Snowball and volunteer sampling can access hard-to-reach groups but results will not be generalizable due to non-representativeness. Convenience sampling is cheap and easy but results in a biased sample.

1. Methodology:
Sampling
methods.
LO: To understand the different
types of sampling methods and
the strengths and weaknesses of
these methods.

2. Key Words
Activity

3. 1. Closed questions

4. 2. Questionnaires

5. 3. Variables

6. 4.Representative

7. 5. Sampling

8. 6. Sampling Frame

9. Starter: Write down as
many of the key words
that you can remember
from the presentation (6).

10. 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

11. • 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

12. 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.

13. How do you choose people
to research?
• Sampling is how you choose
individuals to research.
• There are 6 different types of
sampling.

14. 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.

15. What could be the strengths and
weaknesses of this method?
Strengths Weaknesses
•Avoids bias/ •Not a representative
subjective sampling type,
judgements of who to people with certain
include. variables could get
•Everyone has equal left out, i.e.
chances of being accidentally you could
selected. choose all men-
Implications for your
findings?

16. 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.

17. What could be the strengths and
weaknesses of this method?
• Similar to random sampling.

18. 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?

19. Strengths and weaknesses
of quota sampling
Strengths Weaknesses
1. Simple, quick and 1. Bias, the people are
easy. selected on appearance,
so people may be
2. You can get people excluded.
with the desired 2. The sample will differ
characteristics e.g. depending on the time of
gender, ethnicity, age. 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.

20. 4. 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

21. 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?

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

23. 4. Strengths and weaknesses
of stratified sampling
Strength Weakness
1. Provide a 1. Can only use this form of
sampling if you have the
representative required information to
sample, as the draw the sample, which
sample is selected can be difficult to obtain.
E.G Electoral registers can
on the basis of the be used as a sampling
required variables. frame, yet if you wished
to study religion they
would be of no use.

24. 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.

25. What are the advantages and
disadvantages of snowball sampling?
Strengths Weaknesses
1. Can access people who are 1. The sample will not be
difficult to access. i.e. if there is representative as it relies on
no present information for a personal recommendation.
sampling frame, or if the group 2. Will not be able to make
is so small that normal sampling generalisations as sample is
methods would not access not representative.
them.
2. Can access groups of like
minded people who do not wish
to be identified i.e. drug users.

26. 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.

27. 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