Psych - Research Methods

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Experiment

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A research method used to test a hypothesis about a cause-effect relationship, where the cause is the independent variable and the effect is the dependent variable, in controlled conditions.

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Independent variable

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What is being manipulated by the researcher, the variable of interest to the researcher

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Dependent variable

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What the researcher measures - a measure of effect of the IV

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Extraneous variable

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A variable that may affect the DV apart from the IV and so spoil the experiment.
(e.g. intelligence, education)

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Confounding variable

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A variable that consistently changes with the IV. If present, no conclusion can be drawn.
(e.g. the control group is entirely male, and the experimental group entirely female)

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Individual participant differences

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• A kind of extraneous or confounding variable
• Uncontrolled personal characteristics or experiences of individual participants that may impact the DV (e.g. age, gender, intelligence)
• This can be minimised or controlled by using a repeated measures or matched participants experimental design

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Order effect

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• A kind of extraneous or confounding variable
• When a participant’s performance is influenced by the order in which treatment is presented
• (e.g. a person performs better in the second task because they had practise in the first, or a person performs worse in the second task because they became fatigued from the first)
• Can be managed with counterbalancing, or using an independent groups experimental design

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Counterbalancing

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Systematically changing and presenting the order of treatments or tasks in a ‘balanced’ way, in order to counter unwanted order effects

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Operational hypothesis

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Hypothesis that specifies how the variables will be tested in the research study.
• The IV and DV are operationalised (made testable)
• The population is stated

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Kinds of sampling

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• Convenience sampling: sample chosen on the basis of availability to the researcher, likely that the sample is not representative of the population
• Random sampling: every person in the population has an equal chance of being selected, good chance of unbiased, representative sample
• Stratified sampling: target population is divided into strata (subcategories based on relevant characteristics), participants are selected from each stratum in the same proportion that they appear in the target population

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Random allocation

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• Participants are randomly allocated to the control group or the experimental group
• Ensures that groups are fairly equivalent in personal characteristics, and minimises the effects of extraneous variables

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Control group

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The group that is not exposed to the IV, and is used as a comparison for the experimental group.
Determines whether any changes in the dependent variable that are obtained are likely to occur as a normal part of the behaviour of the participants in the experiment.

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Independent groups experimental design

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Each participant is allocated to only one of the groups in the experiment
Strengths
• Quick, easy and cheap
• You can use all the participants
• No order effects
Limitations
• Little control over participant variables - we assume the groups will be equivalent by chance variation

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Repeated measures experimental design

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Participants are involved in both experimental and control groups
Strengths
• Control over participant variables
• Fewer participants needed
Limitations
• Order effects (counterbalancing can't always be used)
• Demand characteristics - they may figure out what the experiment is about, and this may affect performance

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Matched participants experimental design

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Participants are matched with someone similar to them in relevant characteristics that may influence the DV (experience, intelligence), and one is put into the control group, and the other in the experimental group
Strengths
• Control over participant variables
• No order effects
Limitations
• Time consuming and potentially more expensive
• Loss of unmatched participants (can't necessarily all be used)
• Need more participants