Sampling (Pg 156-157)
The purpose of nomothetic psychological research is to gain results which can be then generalised beyond
the participants of the study. There is little point in carrying out research which only applies to the people
who took part in the study.
In psychology, we draw a sample of participants from a target population. A target population is the group
of people we wish to investigate. The aim is to gain a sample which is representative of the target
population. This is called a representative sampling. If the sampling methods we use provide us with a
representative sample, we can generalise back to our target population, and be relatively sure that results
which apply to our sample will hold true.
Target
Population
Representative
Sampling
Sample
used in
study
Results
generalised
Target
Population
For example, if we wished to investigate drug use in British teenagers it would be impractical to
carry out a study on our target population of every single British teenager. We would select a
sample of teenagers from the target population. If that sample is representative, we can
generalise the results from our small sample, back to the target population
Target population
The target population can be specific, such as a type of profession (teachers, nurses),
people with a specific mental illness (schizophrenia, depression), a certain type of
lifestyle (smokers, drivers) etc. However, often in psychology, the target population
is more general. Psychologists are often looking for results that can be generalised
to all humans!
Sampling techniques
There are a number of ways psychologists can identify and select participants for their experiment.
TASK
Using the information on pg 156-157 cut up the squares on the handout. Organise them on a sheet of A3 under
the following headings
Name
Description
Strengths
Weaknesses
It is important to note however, that regardless of the method used, there is always the issue that some
participants may refuse to take part in an experiment. This would leave a biased sample, as those that do not
want to take part will be different from those that do.
A note about contextualising...
In section C of the exam, you will be given a choice of two stimulus materials to choose from. These will be
two made-up examples of psychological research. You will be given some questions based on this material,
and for full marks your answers must be applied to the material (hence applied research methods). This
means that you must refer to the stimulus material in your answer.
For example:
A psychologist is investigating the effect of reading on general intelligence in school children. He puts
together an alphabetised list of all the school children in the county, and uses a computerised system to
chose 50 students in an random way.
Q1: Identify the sampling method used, and give one advantage and one disadvantage of this method
in this study [3]
Answer 1
A random sampling method was used. An advantage of a random sample is that it avoids any bias
in selecting participants. All members of the target population have an equal chance of being chosen
for the sample. A disadvantage is that the researcher may still end up with a biased sample if the
sample size is too small.
While this answer demonstrates that the student understands the concepts of sampling, none of the answer
has been applied to the stimulus material. Therefore, this would only get 1/3.
Answer 1
The sampling method used in this study was random sampling. An advantage of a random sample
in this experiment is that all of the children in the county have an equal chance of being chosen for
the study. This should produce a sample of children which is representative of the target population.
A disadvantage is that the sample size is only 50. This means that even with random sampling, the
researcher may end up with many more boys than girls for example.
This is a much better answer. The student has applied the knowledge about sampling to the stimulus
material, stating how the advantage or disadvantage is relevant to the study given. This would get 3/3
TASK
For the following, identify the sampling method used, and give one advantage and one disadvantage of this
method in this study (your answer must be contextualised)
a) A researcher wishes to test the memory of children aged between 5 and 11 years old. He contacts the
headmaster of a local school and arranges to test the children.
b) A group of psychology students decided to interview shoppers in the town centre about attitudes
towards dieting. They ensured that they identified people from each age group.
c) A university wishes to test attitudes towards exams. A poster is put in the student common rooms
which direct students towards a website where they can fill in a survey.