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1.3 Research in Psychology: Experimental Methods. Pgs. 25 - 29. The Use of Experiments in Psychology. GOAL: establish cause and effect relationship between two variables Experiment: Quantitative research (generates numerical data) Variables

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The use of experiments in psychology
The Use of Experiments in Psychology

  • GOAL: 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.

Apply your knowledge pg 26
Apply your knowledge – pg 26

  • 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 playground

    • 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 aggression.

The experiment
The Experiment

  • 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.

Be a thinker pg 27
Be a Thinker pg 27

  • Identify the IV and DV in each of the experimental hypotheses:

  • 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 negatively.

  • 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.

Different kinds of experiments
Different Kinds of Experiments

  • Laboratory experiments

  • Field experiments

  • Natural experiments

Laboratory experiments
Laboratory 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 setting?

Field experiment
Field Experiment

  • 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 Genevese1964

    • The bystander effect

  • Cons

    • Cannot control all variables

Natural experiment
Natural Experiment

  • 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

Points to consider with experiments
Points to consider with experiments

  • ConfoundingVariables: 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

Points to consider with experiments cont
Points to consider with experiments cont.,

  • 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.

      • To overcome – Single Blind control – participants do not know what the study is about.

    • Researcher Bias or observer bias- the researchers sees what he wants to see.

      • To overcome – Double Blind control – the participants & researcher do notknow who is in the control group vs. experimental group

    • Participant Variability – sample represents same characteristics

      • Overcome – random sampling

Correlation studies
Correlation studies

  • 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.

Advantages of correlation studies
Advantages of Correlation Studies

  • They are simple and provide a numerical representations of the relationship that can be easily understood

  • They allow the study of a number of variables that cannot be manipulated experimentally.