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Experimental methods. Learning objectives. By the end of this section students will be able to:. Describe the scientific approach to the study of behaviour State the main features of laboratory experiments, field experiments, online experiments and quasi experiments.
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Learning objectives By the end of this section students will be able to: • Describe the scientific approach to the study of behaviour • State the main features of laboratory experiments, field experiments, online experiments and quasi experiments. • Evaluate each experimental method. Icons key: For more detailed instructions, see the Getting Started presentation Flash activity (not editable) Teacher’s notes (in Notes Page) Accompanying worksheet Sound Video Web links Extension activity
The experimental method All experiments are designed around the experimental method. It is a method used by scientists to test hypotheses. participants randomly allocated to conditions a change in the dependent variable,which ismeasured by the experimenter independent variable manipulated by experimenter extraneous variables are controlled Psychologists use three types of experiments to investigate behaviour: laboratory, field and natural experiments.
Online experiments This is a new way of collecting data. Participants are collected through the internet or social media. Anyone can visit sites such as www.socialpsychology.org to become a participant; often taking part in questionnaires.
Quasi-experiments • There are two kinds of quasi-experiments: • Natural experiments (with an IV) • Differences studies (no IV) • You’ll now watch an animation on natural experiments and make notes in your booklet.
Difference studies • The IV is naturally occurring and a DV can be measured in a lab. The IV has not been made to vary by anyone. • An example is studies of gender differences in obedience, or smelling (olfactory) abilities of sighted and non-sighted children.
Class discussion A psychologist wants to investigate the effect of chocolate on the performance of students. How could the psychologist test this? What variables need to be controlled? How could they be controlled? What experiments could be performed? Suggest laboratory, field and natural experiments he could perform. What are the advantages and disadvantages of each type of experiment?
2 2 2 2 2 1 1 1 1 1 Experimental Design Independent Groups Design Participants only take part in one condition of the experiment (2 separate groups) Weaknesses: More ppts are needed than repeated measures design. Differences between participants in the groups may affect results, (participant variables). Strengths: Avoidsorder effects. Less demand characteristics Matched Pairs Design Participants are matched in each condition for characteristics that may have an effect on their performance. e.g. age, gender, IQ etc. Weaknesses: Very time-consuming trying to find closely matched pairs. Impossible to match people exactly. Requires more participants. Strengths: Reduces participant variables. Avoids order effects. Repeated Measures Design Participants take part in both conditions of the experiment (1 group). Weaknesses: Order effects are more likely to occur (counterbalancing needed). Demand characteristics more likely as participants might guess the aim of the study. Strengths: Avoids the problem of participant variables. Fewer people are needed. Words Words Pictures Pictures
Practice questions • Explain what is meant by independent groups design. (2) • Name one other type of experimental design and explain how it might be used. (2) • Explain one disadvantage of using matched pairs design. (3)
