1. Sampling To conduct a study, a psychologist needs participants
A participant is someone who takes part in a study
A group of participants is known as a sample
There are a number of ways to select a sample…
Activity: Think of as many ways as you can to gather a sample

2. Generalise…
The extent to which findings can be applied to those who were not originally tested on

3. Representative…
Example: a representative is drawn from a population of interest and has demographics and characteristics that match those of the population in as many ways as possible.
If you wanted to look at the UK, you would have to include participants with a range of ages, genders, religions, cultural backgrounds etc.

4. Obviously it is not (usually) possible to test everyone in the target population so therefore psychologists use sampling techniques to choose people who are representative (typical) of the population as a whole. =
If your sample is representative then you can generalise the results of your study to the wider population.

5. Sampling technique Common Room Opportunity sample
People who are there at the time
It consists of taking your sample from the people who are available at the time the study is carried out and who fit the criteria you are looking for
Common Room
Opportunity:
 Quick / Cheap / Easy
Not representative
could pick people who
they think will help support
their hypothesis

6. Self-selected (volunteer) sample
When individuals respond to an advert
Volunteers needed for psychological study on learning
I just love to be helpful….
I’ve always wanted to be in a study….
Sounds rubbish…
Gotta do my hair..
Volunteer
Quick / Cheap / Easy
Not representative
May get a certain type of person
Psych Lab
Saturday, 23 February 2019Saturday, 23 February 2019

7. Stratified sampling = 60% female = 60% female 40% male 40% male
More representative 
Time consuming 
This involves the population into categories and then choosing a sample which consists of participants from each category in the same proportions as they are in the population.

8. Snowball sample
This is when a psychologist studies an individual and then asks that individual if they have any (similar) friends who would like to take part.

9. Random sample Everyone has equal chance of being selected
This involves identifying everyone in a target population, then selecting the number of participants you need
 Expensive and time consuming
 Not always possible to get complete list for target population
 Representative sample

10. Questions
Which Skittles would I choose if I were going to take an opportunity sample?
How would I choose a random sample of Smarties?
How would I get a self-selecting sample?
How would I get a stratified sample?
Give smarties
1. The whole tube as they are there
2. Names in a hat
3. The ones which volunteer
4. Categories – colours – one from each

11. There should be 16 Skittles in each pack
There should be 16 Skittles in each pack. There are five different colours. For equal distribution, there should be three of each colour in each pack (+1 extra).
Are there 16 in your pack?
Is there an equal number of each colour?
Is your pack representative of the whole Skittles population?

12. Is the sample representative?
Ideally a sample would accurately represent the target population. For example, if my target population was the UK then I would need to include different genders, ages, races, etc.
Can you say your pack of Skittles are representative?
Is the sample generalisable?
If your sample is representative then it means you can generalise from your sample to your target population (i.e. the results can be applied to other people from your target population).
Can you say your pack of Skittles are generalisable?

13. Using your Skittles, calculate the central tendency
Central tendency is a way of analysing results so you can see the average that the set of values has. There are three main measures of central tendency:
Mean – Adding up all numbered data in a finding and then dividing it by the number of participants.
Median – Ranking all the data from lowest to highest and then choosing the score that lies in the centre.
Mode – Selecting the number that most frequently occurs in a set of data.

14. Draw a graph showing the mean of each colour from all packets
Mode
Median
Purple
Green
Orange
Yellow
Red
Draw a graph showing the mean of each colour from all packets