1. Psychological Research method
EXPERIMENTS
Psychological Research method

2. Key Terms – Experiments Please complete these definitions on your worksheet as you go
Ethics
Informed consent
Right to withdraw
Independent Measures
Repeated Measures
Matched-Pairs
Counter Balancing
Operationalising Hypothesis
Alternative Hypothesis
Null Hypothesis
descriptive statistics (mean, median, mode, range)
bar chart
Laboratory Experiment
Field Experiment
Quasi Experiment
Independent Variable
Dependent Variable
Control of variables
Confounding Variable
Extraneous Variable
Replication
Cause and Effect
Ecological Validity
Demand Characteristics

3. Experiments Three types of experiments: Laboratory experiments
Highly controlled / artificial
Field experiments
Controlled variables in a natural environment
Quasi (natural) experiments
We have no control over the independent variable – it’s ‘naturally’ occurring (eg Gender)

4. Experiments Independent Dependent Variable Variable
(IV) ~ the variable we manipulate / change
Dependent
Variable
(DV) ~ the variable that we measure
Extraneous Variable: a variable that could affect the DV but
has been controlled for so it doesn’t.
Confounding Variable: a variable that effects the DV

5. Experiments Single Blind – Double Blind – Control Groups
Extraneous Variables
Participant Variables
Independent Measures = Individual Differences
Situational Variables
Any feature of the experiment that could influence a participants behaviour
Single Blind – Double Blind – Control Groups

6. Experiments – Hypotheses
How are we measuring memory?
What’s better or worse? Higher / Lower? More / Less?
Participants memory will be much worse when there is a distraction in the room than when there is no distraction.
Participants memory will be much worse when there is a distraction in the room than when there is no distraction.
What is the distraction? How are we manipulating it?
Operationalising your hypothesis
How have you manipulated your IV?
How have you measured your DV?

7. Experiments – Hypotheses
Participants memory will be much worse when there is a distraction in the room than when there is no distraction.
Participants will remember significantly more words from a list of 20 presented for 60 seconds when they are in a room with no distractions than participants who are in a room where rock music is playing in the background.

8. Experiments – Hypotheses
Participants who [do something] will be significantly [faster/better/quicker etc] at [something] than participants who [do something else].
There will be no significant difference between participants who [do something] and those who [do something else]. Any difference will be down to chance.
Alternative
Null

9. Experiments – Hypotheses
Participants who [do something] will be significantly [faster/better/quicker etc] at [something] than participants who [do something else].
There will be a significant difference between participants who [do something] and those who [do something else].
1Tailed
2Tailed

10. Sampling General Population Representative Sample Generalisations
Sampling Techniques
Sample

11. Sampling Opportunity Sample People who are there at the time.
Quick / Cheap / Easy
Not representative
Random Sample
Each person in the GP has an equal chance of being chosen.
Expensive and time consuming.
Representative sample

12. Sampling Self-Selected
Participants volunteer to be in the sample following advert etc.
Quick / Cheap / Easy
Not representative
What kind of person volunteers for a psychology experiment?
Snowball Sampling
One person tells others who tell others …
Allows us to collect difficult to locate people
Time consuming

13. Experiments Repeated Measures Independent Measures
Participants are only in one condition.
Repeated Measures
The same participants repeat the two conditions
Condition 1 Condition 2
Condition 1 Condition 2
Counter balancing – alter order of Pp’s

14. Experiments
Matched Pairs – make two groups of participants as similar as possible.
Condition 1
Condition 2
Male (Bob) 21
IQ = 105
Male (Richard) 21
IQ = 105
Female (Dawn) 25
IQ = 115
Female (Cara) 25
IQ = 115

15. Strength Weakness Independent Measures Repeated Measures Matched Pairs
No Order Effects Fewer Demand Characteristics
Individual Differences
Repeated
Measures
No Individual Differences
Order Effects
(counter balancing)
Matched
Pairs
Controls for Individual Differences
Can be difficult and costly.
Evaluation of Experimental Designs

16. Ethics Debriefing Deception – can not! Right to Withdraw
Informed Consent
Protection from physical and psychological harm
Additional considerations:
Confidentiality
Observation
Advice
Colleagues

17. Scattergram to show the Correlation between variable
Data Analysis
Scattergram to show the
Correlation between variable
1 and variable 2
Titles are VERY important. Title your axis, the integers and give the graph a title.

18. Data Analysis Descriptive Statistics
Summary of data to illustrate patterns and relationships – BUT can’t infer conclusions
Inferential Statistics
Statistical tests that allow us to make conclusions in relation to our hypothesis.
eg. Mann-Whitney or Spearman’s Rho.

19. Ethics Cause & Effect Types of Experiments Sampling Methods
Independent & Dependent Variables
Confounding & Extraneous Variables
Cause & Effect
Types of Experiments
Laboratory
Field
Quasi (natural)
Experimental Methods
Independent Measures
Repeated Measures
Matched-Pairs
Sampling Methods
Opportunity
Random
Snowball
Stratified
Self-Selected
Ethics
Ecological Validity
Reliability
Validity