1. Lesson 02: Experimental Design
Research Methods
Lesson 02: Experimental Design

2. Task 1: Designing an experiment…
Starter: Design an experiment to test the following:
You want to investigate gender differences in the speed of texting on mobile phones in order to see who are the fastest, males or females.
Make sure you consider everything you have learnt about Research Methods (RM) so far…
Aim – Your research question?
Your operationalised IV & DV
Method – Including:
The Design (Laboratory, Field)
Participants (Sample)
How will you recruit your participants? How will you divide your participants in the study?
Materials required
The procedure
Make sure you can explain all of your choice – you need to be able to justify why you experiment is the best!

3. Learning Objectives:
Compare & contrast the following experimental designs:
Independent group design
Repeated measures group design
Matched pairs group design
Identify which experimental design is used within psychological research.
Detail the advantages & disadvantages of different experimental designs.

4. What is meant by experimental design?
If you have decided that an experiment is the best approach to testing your hypothesis, then you need to design the experiment.
Experimental design refers to how your participants are allocated to the different conditions in an experiment.

5. Experimental Design…
Experimental design refers to how we use/allocate our participants in our experiment.
There are three main ways that participants can be allocated:
Independent measures
Repeated measure
Matched pairs
These Jelly Babies are now your participants…

6. Independent Measures
Different participants are used in each condition of the experiment.
This should be done by random allocation, which ensures that each participant has an equal chance of being assigned to one group or the other.
Independent measures involves using two separate groups of participants; one in each condition.

7. Concentration on a reading test.
Independent Measures
You want to test how noise will affect concentration in a reading test. Task 2: Arrange your Jelly Babies to test the above statement, allocating your ‘participants’ according to an independent measures design…
Group 1
Group 2
Concentration on a reading test.

8. Concentration on a reading test.
Independent Measures
Participants A B C D E
Condition 1
Participants
Concentration on a reading test. F
G H I J
One the mini-whiteboards, detail one strength and one weakness of using an independent groups design.
Condition 2

9. Advantages & Disadvantages
Avoids order effects (such as practice or fatigue) as people participate in one condition only. If a person is involved in several conditions they man become bored, tired and fed up by the time they come to the second condition, or become wise to the requirements of the experiment!
DISADVANTAGES:
More participants are required and therefore the design is more costly and time consuming.
Differences between participants may affect results, for example; variations in age, sex or social background. These differences are known as participant variables (i.e. a type of extraneous variable).
Were all of your Jelly Babies the same in terms of age, sex, social background…

10. Repeated Measures
The same participants take part in each condition of the experiment.
This means that each condition of the experiment includes the same group of participants.

11. Concentration on a reading test.
Repeated Measures
You want to test how noise will affect concentration in a reading test. Task 3: Now, arrange your Jelly Babies to test the above statement, allocating your ‘participants’ according to an repeated measures design…
Group 1
Group 2
Concentration on a reading test.

12. Concentration on a reading test.
Repeated Measures
Participants A B C D E F G H I J
Condition 1
Concentration on a reading test.
One the mini-whiteboards, detail one strength and one weakness of using a repeated measures design.
Condition 2

13. Advantages & Disadvantages
Fewer participants are required as they take part in all conditions (i.e. saves time)
DISADVANTAGES:
There may be order effects.
Order effects refer to the order of the conditions having an effect on the participants’ behaviour. Performance in the second condition may be better because the participants know what to do.
How might we combat ‘order effects’?
COUNTERBALANCING:
To combat order affects the researcher counter balances the order of the conditions for the participants. The sample is split in two groups experimental (A) and control (B). For example, group 1 does ‘A’ then ‘B’, group 2 does ‘B’ then ‘A’ this is to eliminate order effects – the participants are counter balanced.

14. Matched Pairs
Pairs of participants are matched from participants in terms of key variables, such as age and IQ. One member of each pair is then placed in the Experimental group and the other member in the Control group.

15. Concentration on a reading test.
Matched Pairs
Participants
Participants A B C D E A B C D E
Condition 1
Condition 2
One the mini-whiteboards, detail one strength and one weakness of using a matched pairs design.
Concentration on a reading test.

16. Advantages & Disadvantages
Reduces participant variables because the researcher has tried to pair up the participants so that each condition has people with similar abilities and characteristics.
Avoids order effects, and so counterbalancing is not necessary.
DISADVANTAGES:
Very time-consuming trying to find closely matched pairs.
Impossible to match people exactly, unless identical twins!

17. Applying Experimental Design
For each of the following studies answer the following questions :
State the operationalised IV and the DV of the experiment
Name the conditions
State which experimental design has been used
Give one strengths & weakness of that design, specific to the study
1) A psychologist wants to test the theory that doctors have better spatial awareness than teachers. A group of doctors and teachers are given a series of spatial awareness tasks (such as rotating a cube in their heads, giving directions on a map etc.) which produces a spatial awareness score.

18. Applying Experimental Design
For each of the following studies answer the following questions:
State the operationalised IV and the DV of the experiment
Name the conditions
State which experimental design has been used
Give one strengths & weakness of that design, specific to the study
2) It is proposed that people are more willing to give money to a male rather than a female charity collector. This is tested by showing participants photographs of male and female faces and a description of a fake charity that they represent. The participants are then asked to say how much (if any) money they would donate.

19. Applying Experimental Design
For each of the following studies answer the following questions:
State the operationalised IV and the DV of the experiment
Name the conditions
State which experimental design has been used
Give one strengths & weakness of that design, specific to the study
3) A psychologist wants to test the theory that doctors have better spatial awareness than teachers. A group of doctors and teachers are given a series of spatial awareness tasks (such as rotating a cube in their heads, giving directions on a map etc.) which produces a spatial awareness score.

20. Applying Research Methods…
You will now apply everything you have learnt about research methods to the following studies…
Bahrick (1975)
Bower (1969)
Godden & Baddeley (1975)
Loftus & Palmer (1974)
Maguire (2000)
Peterson & Peterson (1959) 1. 2.
Aim – The research question?
The operationalised IV & DV
Method – Including:
The Design (Laboratory, Field)
Participants (Sample)
What experimental design was used? Do you think this was the best choice and why?
Materials required
The procedure
Results – What were the key %s found?
Conclusion – One sentence, summarising the results, linked to the original aim. 3. 4. 5. 6.

21. Experiment 1 - Recap
An experimenter wants to see if drug X improves sport performance. One group are given the drug, another are given a placebo. Both groups are tested for athletic ability.
Identify the IV and DV;
Identify the experimental condition and the control condition.

22. Experiment 2 - Recap
A researcher is interested in whether alcohol has an effect on memory. One group of participants are given a list of words to learn and then given an alcoholic drink. The other group is given the same list of words, and a glass of water. The number of words they can remember is recorded.
Identify the IV and DV;
Identify the experimental condition and the control condition.

23. Experiment 3 - Recap
A psychologist is investigating the effect of music on concentration. A group of participants are given a series of crossword puzzles to solve, first in a silent room, then when classical music is played, and then when rock music is played. The time taken to solve each puzzle is recorded.
Identify the IV and DV;
Identify the experimental condition and the control condition.

24. Experiment 4 - Recap
A scientist has developed a drug which he believes will increase IQ. He has two groups of participants; one group he gives the drug to, and the other he gives a placebo to. After two weeks, he tests their IQ. To try and avoid any participant variables, he ensures that he has an equal number of men and women in each group, and that the participants are of similar ages, intelligence and social background.
Identify the IV and DV;
Identify the experimental condition and the control condition.