A writeup on experiments as part of research methods for OCR Psychology A-Level, including types of experiments, variables, strengths and weaknesses, experimental design and more.
Experiments
Types of experiment:
There are three main types of experiment, each with their own advantages and
disadvantages.
Laboratory experiments:
The IV is manipulated by the researcher and the experiment is carried out in a laboratory or
other contrived setting away from the participants’ normal environment.
Advantages:
- Highly controlled
- High internal reliability
- Little to no extraneous variables
- Cause and effect
Disadvantages:
- Possibility of demand characteristics
- Low ecological validity due to unnatural setting
- More effort, time and money in order to conduct research
Field experiments:
The IV is manipulated by the researcher but this time the experiment is carried out using the
participants in their natural surroundings.
Advantages:
- High ecological validity
- Less chance of demand characteristics
- High internal validity
- Less effort to set up and conduct
Disadvantages:
- Harder to get consent, especially informed consent
- Lower internal reliability due to less controls
Quasi experiments:
Also called natural experiments, the IV is naturally occurring (e.g., weather, cloudy
conditions vs sunny conditions), not manipulated by the researcher.
Advantages:
- High ecological validity
- Helps us study variables we cannot manipulate
, Disadvantages:
- Difficult to conduct in some conditions
- Cannot control some participant variables that may influence the results
Conditions:
In an experiment, there are normally two conditions, the experimental condition (has
experienced change or manipulation) and the control condition (has not experience change
or manipulation.
Single/double blind:
Research might be single or double blind as a strategy to avoid bias or demand
characteristics. Single blind means the participants do not know the aim of the study,
reducing risk of demand characteristics. Double blind means both the participant and the
researcher are blind to the aim of the research, eliminating the risk of researcher bias.
Experimental design:
There are three main ways to design an experiment.
Repeated measures:
This involves using the same people for each condition of the experiments.
Advantages:
- Less effort to obtain sample
- Shows how one individual responds to two settings
- Can remove the effect of participant variables
Disadvantages:
- People may present demand characteristics
- Order effect may influence results.
Independent measures design:
This involves using different people in each condition.
Advantages:
- Reduces risk of demand characteristics
- No order effects with one condition
Disadvantages:
- More effort to obtain sample
- There could participant variables in the way.
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