• All homework assessments to go in your folder
in order.
• With a homework cover sheet
• Chose a piece of homework to make
improvements on. Use a different colour or
clearly label it DIRT.
• Update the homework cover sheet,
Dedicated, Improvement & Refection Time (DIRT)
• You do the work
• You get the Feedback
Respond to any questions
Look up answers in the textbook
Ask a friend or compare your
work to theirs
• You get time to respond to the feedback and make
improvements.
• If it is not excellent it is not finished
• You move your work closer to excellence
I can
 Explain how to control extraneous variables
 Distinguish between directional & non
directional hypotheses
 Construct operationalised hypotheses
 Name and evaluate different sampling methods.
 Name and evaluate three experimental designs
 Name and evaluate lab, field and Natural
experiments
 Distinguish between Reliability & Validity
A03 - How Science Works
Observe human behaviour
Develop explanations (theory)/hypotheses
Test hypotheses
Collect results/data
Analyse data/graphs/inferential statistics
Draw conclusions
What is an experiment?
A research method in which:
• There is an independent variable (IV)
manipulated by the researcher .
• The effects of the IV on another variable are
observed or measured. This variable is called
the dependent variable (DV).
• The participants are allocated randomly to the
conditions.
Experimental method
PPs revise using
concept maps
Test of
learning
Score
Test of
learning
Score
Conditions
PPs revise using
note-taking
IV
DV
Methods
Experimental
• Lab
• Field
• Natural
Non Experimental
• Case study
• Correlation
• Observations
• Interview
• questionnaire
Extraneous Variables
Explain how to control extraneous variables
Control of Extraneous variables
Psychologists try to control extraneous variables
so that they don’t become confounding
variables.
Extraneous variables can impact on the internal
validity of a study. If they are not controlled they
can confound the results because the change in
the DV may be due to the extraneous variables
rather than IV
Explain how to control extraneous variables
Caffeine
Number of words
recalled
Explain how to control extraneous variables
Caffeine
Number of words
recalled
Explain how to control extraneous variables
Caffeine
Number of words
recalled
Explain how to control extraneous variables
Controls
There are 3 types of variables to control.
Participant variables
Situational variables
Experimenter variables
Explain how to control extraneous variables
Explain how to control extraneous variables
Explain how to control extraneous variables
Explain how to control extraneous variables
Controls for
Situational Variables
1. Standardise – keep everything
the same for each participant
Standardised Procedure
Standardised Instructions
Explain how to control extraneous variables
Explain how to control extraneous variables
Controls for Situational
Variables
2. Counterbalance – to reduce effect of
situational variables or order effects
This
“balances”
out
any
order
Split the
group
in half 1 > 2
Group
1 do
condition
effects.
E.g.
If
you
do
better
Group 2 do condition 2 > 1
on the 2nd test, 50% will do
better in Condition 1 and
50% do better in condition 2
Demand Characteristics
Refers to situation where participants form
an interpretation of the experiment's
purpose and unconsciously change their
behaviour accordingly
Explain how to control extraneous variables
Controls for Demand
Characteristics
Explain how to control extraneous variables
Experimenter Variables
The experimenter effect is a term used to describe subtle
cues or signals from an experimenter that affect the
performance of participants in studies.
The cues may be unconscious nonverbal cues,
such as muscular tension or gestures. They
may be vocal cues, such as tone of voice.
Explain how to control extraneous variables
Controls for Experimenter
Variables
Explain how to control extraneous variables
Mini Plenary
• “Sort it out”
Definition
The EV they attempt to
overcome
Single blind
Double blind
Experimental realism
Standardised procedures
counterbalancing
Explain how to control extraneous variables
Variables
“Carrying more bags or sugar makes you run slower”.
Extraneous and confounding variables
Anything other than the IV that may influence the DV is
an extraneous variable.
We need to control these.
If the dependent variable is influenced then the
extraneous variable has become the confounding
variable
Aims & Hypothesis
I can
Distinguish between directional & non
Directional hypotheses
Construct an operationalised hypothesis
Aims & Hypotheses
Aims: An aim is a general statement of why the study is
being carried out.
Hypotheses: In psychology a hypothesis is:
• A clear statement
• A prediction
• Testable
• Formulated at the beginning of the research process
• A hypothesis to test the idea might be:
Ps will correctly recall more words in a memory test after learning a list of words by
image-linking than Ps who learn the same words via simple rehearsal.
Distinguish between directional & non
Directional hypotheses
Construct an operationalised hypothesis
Hypotheses
Experimental Hypothesis: Used when using the
experimental method
Alternative Hypothesis: Used when not using an
experimental method e.g questionnaire
Null Hypothesis: A null hypothesis predicts that any
differences or similarities between the sets of
results in an experiment are due to chance alone.
• Spot the difference between the following
2 examples of experimental hypotheses:
• 1. There will be a difference in the reaction
times between p’s who have drunk alcohol
and p’s who have drunk water.
• 2. The reaction times of p’s who have drunk
alcohol will be slower that the reaction
times of those p’s who have drunk water.
Distinguish between directional & non
Directional hypotheses
Distinguish between directional & non
Directional hypotheses
Distinguish between directional & non
Directional hypotheses
Directional & Non Directional
Hypotheses
Mini Plenary: Directional & Non Directional?
Distinguish between directional & non
Directional hypotheses
Operationalising a hypothesis
Hypotheses must be operationalised- this means writing it in a
way that the IV & Dv are defined.
To investigate the relationship between social class and
intelligence
To investigate the relationship between social class as defined by
annual family income and intelligence as measured by
performance on a standard IQ test
TASK Construct and operationalised hypthesis for this
“People remember more when they study in short
bursts”
Construct an operationalised hypothesis
To describe three types of experimental
Methods and give strengths and weaknesses of
them.
Types of Experiment
• Laboratory experiments
• Field Experiments
• Natural Experiments
LAB V FIELD
Come up with some strenghts and weaknesses
of Lab & Field experiments
Strengths and weaknesses of Lab
Experiments
Well controlled.
Permits us to study cause
and effect.
Confounding variables
minimised.
Can be replicated
(copied/repeated)
Ethical Issues
Deception
Informed consent (is it truly
voluntary?)
Psychological harm
Artificial or contrived.
Participants know they are being
studied, which is likely to affect
their behaviour. (demand
characteristics)
Investigator may influence
results.
The setting is not like real life –
low in mundane realism.
it doesn’t represent real-life
experiences e.g. trigrams to test
memory
Low ecological validity
Strengths and weaknesses of Field
Experiments
Permits us to study
cause and effect.
Less artificial so have
higher ecological
validity, (Easier to
generalise from
results.)
Avoids some
participant effects
(when they are
unaware of study)
Less control of extraneous
variables.
More time consuming, so
more expensive.
Ethical Issues
Informed consent
Difficulty debriefing
Privacy
Natural Experiments
• The IV has not been deliberately manipulated
by the experimenter, so the situation is
described as ‘natural’.
• This method used when there are IV’s that
cannot be manipulated directly for ethical or
practical reasons.
• Not true experiments – quasi experiments,
because IV not changed deliberately to see
effect on DV.
Strengths and weaknesses of Natural
Experiments

Allows research where IV
cannot be manipulated for
ethical or practical reasons e.g.
deprivation studies
 Enables psychologists to study
‘real’ problems e.g the effects
of disaster on health –
(increased mundane realism
and ecological validity)
 Less chance of demand
characteristics or experimenter
bias interfering.
 Cannot demonstrate causal
relationships because IV not directly
manipulated.
 Many confounding variables (e.g
allocation of participation to groups),
threat to internal validity.
 Can only be used where conditions
vary naturally.
 Participants may be aware of being
studied.
Ethical Issues
Informed consent
Confidentiality
Experimental Designs
I can
Name and evaluate three experimental
designs
Name and evaluate 3 types of experimental designs.
Most simple experiments involve 2
conditions – these are 2 versions of the
independent variable. e.g. Using words
or pictures to learn a list of items.
Condition 1
Condition 2
Words
Pictures
Name and evaluate three experimental
designs
There are 3 different ways to carry out
the experiment with participants. These
are known as Experimental Designs.
Independent measures design
Repeated measures design
Matched pairs design
Name and evaluate three experimental
designs
Participants only take part in one condition of the
experiment (2 separate groups)
Words
Pictures
Name and
evaluate three
experimental
designs
Participants take part in both conditions of the experiment
(1 group)
Words
Pictures
Name and evaluate three experimental
designs
Participants are matched in each condition for
characteristics that may have an effect on their
performance. e.g. A memory test
2
Name and 1
evaluate
three
experimental
designs
1
2
1
2
1
2
1
2
Experimental designs
Aim: To see if music affects the ability to write the
alphabet backwards.
What type of experiment will you use?
What will the IV be?
What will the DV be?
What problems are there with each of the
experimental designs?
How could we overcome the problems?
Name and evaluate three experimental
designs
The colour
pink is so
awesome...
I’m
cleverer
than her!
Name and evaluate three experimental
designs
They think I’ll
remember
pictures better
than words
I got bored the
second time …
Cat
Dog
House
Counterbalancing
In a repeated measures design there may be order
effects. This is when they get bored or fatigued from
doing a repetitive task. Or they get better in condition 2
because they have had practice.
Counterbalancing- split the group in half, half do
condition 1 first then condition 2. then the other half do
2 then 1.
Name and evaluate three experimental
designs
Counterbalance – to reduce effect of
situational variables or order effects
This
“balances”
out
any
order
Split the
group
in half 1 > 2
Group
1 do
condition
effects.
E.g.
If
you
do
better
Group 2 do condition 2 > 1
on the 2nd test, 50% will do
better in Condition 1 and
50% do better in condition 2
Name and evaluate three experimental
designs
Name and evaluate 3 types of experimental designs.
Key Terms
•
•
•
•
•
•
•
•
•
•
Counterbalancing
Experimental design
Independent groups
Matched pairs design
Order effects
Random allocation
Repeated measures design
Single blind
Demand characteristics
Investigator effects
•
•
•
•
•
•
•
Field experiment
Natural experiment
Natural experiment
Independent variable
Dependent variable
Extraneous variable
Confounding variable