1.3 Research in psychology Experimental Methods

Pgs. 25 - 29
establish cause and effect relationship
between two variables
 Experiment:
Quantitative research (generates numerical data)
 Variables
Independent Variable (IV): variable being
manipulated or changed in the study
Dependent variable (DV): the variable that is
being measured
Variables must be Operationalized, i.e. they
must be measurable.
Operationalize your variables by considering
each of the following descriptions and deciding
whether it is an example of aggression or not.
Two men fight over a parking space
A football player kicks the ball into a goal
Two girls give a boy the “silent treatment” on the
A man kicks the back of the car when it will not start
Three students have a heated debate about whether
global warming is happening.
Know write a well worded definition of
The Experimental Hypothesis predicts the
relationships between the IV and the DV
 Null Hypothesis: predicts that there will be no
results or that the results will be due to chance.
 The Control Group has no experimental actions
applied to it.
Accept the null hypothesis
 Refute the null hypothesis
 Except experimental hypothesis if demonstrate effect
due to IV manipulation.
Identify the IV and DV in each of the experimental
People are more likely to make a risky decision when
they are in a group than when they are alone.
An increase in carbohydrates decreases ones ability
to concentrate.
People will react more quickly to an auditory stimulus
than a visual stimulus.
Lack of sleep will affect learning new word
Children who have watched a film with a model
hitting a blow-up doll will exhibit more aggressive
acts toward a blow-up doll than children who have
not watched the film.
 Laboratory
 Field experiments
 Natural experiments
 Pros:
Easy to control
Easy to replicate
 Cons
Artificial environment
What is the ecological value?
Would your result stand up outside of a lab
 Pros
Used in Social Psychology
Takes place in natural environments, but IV is
still manipulated.
e.g. Piliavin and Rodin (1969) helping behavior in
a New York Subway
Kitty Genevese 1964
The bystander effect
 Cons
Cannot control all variables
 Natural
experiment or quasi – the researchers
have no control over the variables
Research on stoke patients
Cannot change gender
Children who have been separated from their
parents due to war
Confounding Variables: undesirable variables that influence the
relationship between the IV and DV.
Artificiality – the situation is so unlikely that one has to wonder if
there is any validity to the study
Three of the most common confounding variables:
Demand characteristics or Hawthorn Effect –
participants behave in a manner that they think they
should to meet the demands of the study.
Researcher Bias or observer bias- the researchers sees
what he wants to see.
To overcome – Single Blind control – participants do not
know what the study is about.
To overcome – Double Blind control – the participants &
researcher do not know who is in the control group vs.
experimental group
Participant Variability – sample represents same
Overcome – random sampling
 Not
all experiments can be carried out,
however, data can reveal relationships
between two variables = Correlations
 Correlation – as one variable changes the
other variable changes. This does not mean
there is a cause and effect.
Positive correlation: as X increases Y increases
Negative correlation: as X increases, Y decreases
 Note
– no IV is manipulated, thus there is not
cause and effect.
1. They
are simple and provide a numerical
representations of the relationship that can
be easily understood
2. They allow the study of a number of
variables that cannot be manipulated

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