1. Research Methods

2. • Define the following terms
• population
• sample
• representative sample

3. Participant selection and
allocation
• Participants are people used in psychological
research
• The way participants are selected for a
research study and allocated to a group is
very important

4. Population
• The term population refers to the entire group
of research interest from which a sample is
drawn.
• What is an example of a population?

5. Sample
• The process of selecting participants for
research is called sampling
• The participants being studied in the
research are called the sample. A
sample is a subsection, or smaller
group, of research participants selected
from a larger group (population) of
research interest.

6. Sample and Population

8. • A sample is a subgroup of the population. Therefore the
sample is smaller than the population.

9. • A sample is a subgroup of the population. Therefore the
sample is smaller than the population.

10. • A sample is a subgroup of the population. Therefore the
sample is smaller than the population.

11. • A sample is a subgroup of the population. Therefore the
sample is smaller than the population.
• It is important that the sample accurately reflects, or is
representative of the population it is taken from. Why?

12. • A sample is a subgroup of the population. Therefore the
sample is smaller than the population.
• It is important that the sample accurately reflects, or is
representative of the population it is taken from. Why?

13. • A sample is a subgroup of the population. Therefore the
sample is smaller than the population.
• It is important that the sample accurately reflects, or is
representative of the population it is taken from. Why?

14. • A sample is a subgroup of the population. Therefore the
sample is smaller than the population.
• It is important that the sample accurately reflects, or is
representative of the population it is taken from. Why?
• A representative sample allows the psychologist to be more
confident in generalising the findings

15. Generalising
• Extending or applying the results for a
sample more widely to the population from
which the sample was drawn

16. Sampling Procedures
The following procedures ensure a sample is
fairly representative of the population it was
taken
• Random sampling
• Stratified sampling

17. Random Sampling
• Random sampling ensures every member of
the population of research interest has equal
chance of being selected as a participant for
a study
• What method could you use to achieve a
random sample?
• Complete random sample? Is it
representative?

18. Stratified sampling
• In some research studies it is important to
ensure that a particular groups in a
population of interest are represented in
their known proportions in that population
• For example, if a psychologist wanted to
understand Australians attitudes to sex
before marriage, they would reasonably
expect that peoples attitude would differ
depending on their religion.

19. Stratified sampling
• Stratified sampling involves dividing the population to
be sampled into distinct subgroups, or strata, then
selecting a different a separate sample from each
strutum (subgroup), in the same proportions as they
occur in the target population.
• Income, age, sex, religion and IQ are examples of
characteristics that may be used as the bais of dividing
a population into a strata

20. Stratified random
sample
• Same as stratified sample, but after the
people within each stratum are identified ,
random samples of proportionate size are
drawn from within each of the strata
(subgroups)

21. Obtaining a stratified
random sample
• Step 1 - Count the total number of people in the population
• Step 2 - Count the number of people in each religious group
• Step 3 - Calculate the percentage of each religion in the
population using the following formula
Number of people in a religion divided by Total number of
people in the population X 100
• Step 4 - Create a stratified random sample of 10 people
based on the percentages (that is proportions) of religions in
the population

22. Revision
• What would you like me to go over on
Thursday?

23. Participant Allocation
Participant allocation involves the way in which
participants are assigned to the various
conditions in a study. This process needs to be
performed in a systematic way so that there is a
balance of participants’ personal characteristics
in the groups, preventing any potential
confounding variables.

24. Control Group
The control group is the group of participants, which is
matched in all ways possible with the subject
characteristics and conditions of the experimental group
except that it is not exposed to the independent variable.
What is the purpose if this group?
This group serves as a baseline measure for comparison
with the experimental group. The control group helps the
researcher to determine if the independent variable did, in
fact, cause an effect on the dependent variable.

25. Experimental Group
The experimental group is the group of
participants, which is matched in all ways possible
with the participant characteristics and conditions
of the control group but is also exposed to the
independent variable. The purpose of the
experimental group is to provide a measure of the
influence in the dependent variable produced by
the intervention.

26. Random Allocation
• In random allocation, participants selected
for the experiment are as likely to be in one
group as the other.
• What is the difference between random
sampling and random allocation

27. • If you were going to perform a MRI scan
on a 14 year old boy, what two ethical
concerns would you need to consider?
This needs to be explained in an extra-
normal video. (5 Marks)