 http://www.holah.co.uk/quiz/experimentalmethodsrevie
w.htm
Lesson objectives
 What is a target population?
 Identify and describe different sampling methods
 Replicate sampling methods using
 Discuss strengths & weaknesses of different sampling
techniques
 Recap on key terminology
 Upcoming assessment briefing
Target Populations
 Psychologists are interested in making ‘general statements’
about behaviour.
 We can’t test every single person in the world, so
psychologists take a sample of people and try and generalise
their findings to the population.
 A psychologist may be interested in a particular group of
people, e.g. Drinking behaviour in 16-19 year olds living in
the UK.
 This would mean that all 16-19 years in the UK would be the
TARGET POPULATION.
Target Populations
 A sample can be collected by psychologists in a number of
different ways.
 You need to be able to consider which of these sampling
methods are the best to use. Obviously it will depend on
the type of research being conducted.
Random
Sampling
Opportunity
Sampling
Volunteer
Sampling
Stratified
Sampling
Skittles Sampling
Record the number of different coloured Smarties
that you collect for each type of sampling.
Random sampling
 Every member of the target population has an equal
chance of being selected.
 Every Skittles has an equal chance of being selected
How do you think we could
select 5 Skittles from our
packet at random?
Systematic Sampling
 A systematic sample involves the researcher choosing the
nth person on the list.
 E.g. You may chose every 5th person from your Psychology
class register
Show me a systematic sample
of every 3rd Skittle in your
packet.
Opportunity Sampling
 An opportunity sample uses participants who are
available at the time of the research being conducted.
 E.g. You may chose the first students that pass you in the
corridor
Without much thought tip your
Skittles onto the table and select
the 6 Skittles that are nearest to
you
Volunteer Sampling
How many green skittles do you
have?
We’ll presume they all volunteer
to take part in our study.
Green
Skittles
Wanted
Extension Tasks
Scenario 1:
A psychologist wants to conduct research into
healthy eating habits in 16-19 year old students
through questionnaires.
Where should she get her sample from?
What type of sampling methods would be best to use
and why?
Extension Tasks
Scenario 2:
A psychologist wants to investigate whether violence
on TV can influence young children to be aggressive.
Where should he get his sample from?
What type of sampling method would be best to use
and why?
Extension Tasks
Scenario 3:
A psychologist is researching whether Psychology
students have better memories than Economics
Students.
Where should she get her sample from?
What type of sampling methods would be best to use
and why?
Extension Tasks
Yes/No game
Students to stick given experiment key concept to their
foreheads and in groups of 5 have to ask questions to
the rest of their group to decide what concept they are.
Questions can only be answered using ‘yes’ or ‘no’
You say we pay