Research Methodology

Types of experiments
         
Laboratory experiment: Artificial environment with tight controls over variables.
Field experiment: Natural environment with independent variable manipulated by researchers.
Natural experiment: Natural changes in independent variable are used - it is not manipulated.

Strenths and limitations

Labrotory

Strengths:	Weaknesses:
Tighter control of variables. Easier to comment on cause and effect.	Demand characteristics - participants aware of experiment, may change behaviour.
Relatively easy to replicate.	Artificial environment - low realism.
Enable use of complex equipment.	May have low ecological validity - difficult to generalise to other situations.
Often cheaper and less time-consuming than other methods.	Experimenter effects - bias when experimenter's expectations affect behaviour.

Field

A field experiment is an experiment; the independent variable is manipulated. Not all field studies are experiments.

Strengths:	Weaknesses:
People may behave more naturally than in laboratory - higher realism.	Often only weak control of extraneous variables - difficult to replicate.
Easier to generalise from results.	Can be time-consuming and costly.

Natural

Strengths:	Weaknesses:
Situations in which it would be ethically unacceptable to manipulate the independent variable.	The independent variable is not controlled by the experimenter.
Less chance of demand characteristics or experimenter bias interfering.	No control over the allocation of participants to groups (random in a 'true experiment').

key terms
Independent variable (IV): Variable the experimenter manipulates - assumed to have a direct effect on the dependent variable.
Dependent variable (DV): Variable the experimenter measures, after making changes to the IV which are assumed to affect the DV.

Confounding Variable: A Confounding Variable is an extraneous variable whose presence affects the variables being studied so that the results you get do not reflect the actual relationship between the variables under investigation. When conducting an experiment, the basic question that any experimenter is asking is: "How does A affect B?" where A is the probable cause, and B is the effect. Any manipulation of A is expected to result in a change in the effect.

Research methodology: A prediction of study outcomes. Often a statement of the expected relationship between two or more variables.

Null hypothesis: The null hypothesis, denoted by H₀, is usually the hypothesis that sample observations result purely from chance.