Psychology
Sampling with
skittles
Resources for Courses
E
Overview
The purpose of this activity is to consolidate knowledge in relation to the five sampling
methods: random, opportunity, volunteer, systematic and stratified. Furthermore, this activity
also provides an opportunity for students to calculate percentages, which is one the
mathematical requirements of the new A-Level.
PL
Resources Required
• Large bag of skittles (one per group, ideal group size of 3-4)
• Sampling with skittles handout (one each)
Teacher Instructions
M
Teaching and Learning Strategy A
Students should be divided into 3s or 4s and provided with one large bag of skittles. Each
student should also be provided with a copy of the ‘sampling with skittles’ handout.
There are six different parts to this activity and therefore each student should be given an
opportunity to take part in organizing and calculating at least one of the sampling methods.
SA
The teacher’s role is to facilitate the activity and ensure that each student is given an opportunity
to take part in the organising and calculating of the different sampling methods. Students may
find the final method – stratified sampling – more difficult and therefore teachers
may wish to assist students, as they approach this task.
Sampling with skittles
Resources for Courses
PL
E
Discussion: Once the students have completed the activity, the following key questions should
be discussed, while considering the strengths and limitations of each of the sampling methods
explored in this lesson:
1 Which sampling method was the most representative of your target population?
2 Which sampling method was the least representative of your target population?
3 Which of the above sampling methods took the longest to complete? Why might this be an
issue for researchers?
4 Were there any sampling methods were you struggled to recruit 25 participants. Why might
this method be problematic in the real world?
5 Which sampling method is the best and why?
M
Stretch & Challenge
• As the stratified sampling method is the most difficult to calculate, this method could be
assigned to a higher ability student.
• To increase the number of maths skills covered, ask the students to express their results as
a fraction also. In addition, the students could calculate the mean, median and mode for a
particular sampling method, for example, opportunity, as this is the most common method
used in psychology.
S
S A
S
S
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sampling with...
Target population
E
Your task is to experiment with the different methods of sampling, using skittles as your
participants. You will create each of the five sample types, recording the number of each
colour skittle you obtain in your sample and the percentage. Thereafter, you will evaluate
your samples, based upon how representative your sample is in relation to the target
population.
Tip all the sweets out of the bag and record how many of each colour there are, in the table
below:
Number
%
PL
Colour
Purple
Orange
Green
Red
Yellow
M
Total
Percentages – divide the number of [purple/orange/green/red/yellow] sweets, by the total
number of sweets and then multiply by 100. Complete this for each colour.
Random Sampling
SA
Pick out 25 sweets at random and record how many of each colour you get, in the table
below:
Colour
Number
%
Purple
Orange
Green
Red
Yellow
Does your random sample represent your target population?
Opportunity Sampling
Tip out the first 25 sweets from the bag. These are the people who are available and willing
to take part in your research. Record the results in the table below:
Colour
Number
%
Purple
Orange
Green
E
Red
Yellow
Volunteer Sampling
PL
Does your opportunity sample represent your target population?
M
Imagine that you have placed a poster up in school, asking for participants to self-select and
take part in your research. You’ll have to imagine that ‘green’ skittles are the most helpful and
willing to take part, followed by ‘yellow’.
SA
The ‘orange’, ‘red’ and ‘purple’ skittles, definitely won’t want to take part! You are still looking
to recruit 25 participants, but if you can’t manage to get 25, you’ll just have to run your
experiment, with as many as you can. Record your results in the table below:
Colour
Number
%
Purple
Orange
Green
Red
Yellow
Does your volunteer sample represent your target population?
Systematic Sampling
Tip all of the sweets out and place them in one line. Then select every 3rd sweet. Record
your results in the table below:
Colour
Number
%
Purple
Orange
Green
E
Red
Yellow
Stratified Sampling
PL
Does your systematic sample represent your target population?
M
You need to create a sample of 25 sweets that is similar to the target population, in terms
of the percentage of each colour.
If 15% of the sweets in your target population are green, you need to ensure that your sample
(of 25) only has 15% of green sweets.
SA
For example: 15% of 25 = (15÷100) x 25 = 3.75. Therefore, you would need 4 sweets to
represent your target population.
Colour
% in target population
Refer back to your first table
Number of sweets needed
for sample
Purple
Orange
Green
Red
Yellow
Does your stratified sample represent your target population?
Evaluating your samples
E
1 Look at the results recorded above. Which sampling method was the most
representative of your target population?
PL
2 Look at the results recorded above. Which sampling method was the least
representative of your target population?
SA
M
3 Which of the above sampling methods took the longest to complete? Why might this
be an issue for researchers?
4 Were there any sampling methods were you struggled to recruit 25 participants.
Why might this method be problematic in the real world?
5 Finally, as a group, decide which sampling method is the best and why?
Best Sampling Method:
Reason: