Experimental Method (OCR A-Level Psychology): Revision Notes

7.1.1 Experimental Method

Experimental Method

The experimental method involves the manipulation of an IV to measure the effect on a DV. Experiments may be laboratory, field, natural, or quasi.

Types of Experiment

Laboratory – conducted in highly controlled environments.

Strengths	Limitations
-High control over extraneous variables. This means any effect on the DV is likely to be a manipulation of the IV. Therefore, the researcher can be more certain about demonstrating cause and effect (high internal validity). -Replication is more possible due to a high level of control. Replication is vital to check to see whether results are valid or just a 'one-off'.	-Can lack generalisability as the lab environment may be artificial and not like everyday life. Low external validity. -Participants are aware they are being tested and may produce demand characteristics. Tasks participants conduct are normally meaningless.

Field – IV is manipulated in a natural more everyday setting.

Strengths	Limitations
-Have higher mundane realism than lab experiments as the environment is more natural. May produce more valid or authentic behaviour. -High external validity as participants are unaware, that they are being studied.	-Loss of control of extraneous variables. Cause an effect between IV and DV is more difficult to establish and precise replications may not be possible. -Ethical issues arise – as participants are unaware that they are being studied, they cannot consent to being studied and this is an invasion of privacy.

Natural – when the researcher takes advantage of a pre-existing variable. The IV is natural, potentially not the setting. The IV would have changed even if the researcher were not interested.

Strengths	Limitations
-Provide opportunities for research that may not have otherwise been undertaken for practical/ ethical reasons. -Often have high external validity as they involve the study of real-life issues and problems as they arise, such as the effect of natural disasters on stress levels.	-Naturally occurring events happen rarely, reducing research opportunities. Also limits the ability to generalise findings. -Participants may not be randomly allocated to experimental conditions. This means that the researcher is less sure if IV affects DV.

Quasi- IV based on an existing difference between people- no one has manipulated this variable (i.e. age)

Strengths	Limitations
Often carried out under controlled conditions and share strengths of lab experiments.	Cannot randomly allocate participants to conditions so there may be confounding variables.