Choice of experiment is dependent on:
- – How much control we have over IV
- – How much control we have over extraneous variables
- – Decision between reliability OR validity
In an experiment:
- – One variable is kept constant
- – Another measured to see if it changes (IV) relative to the variable manipulated by experimenter (DV)
- – Establish a causal relationship between variables
Laboratory experiments
Carried out in an environment that allows high degree of control over extraneous variables, and controls variation of IV and in order to measure changes to DV
- + More confident of relationship between IV + DV being casual
- + High degree of control = method more easily reliable = method is reliable
- – High degree of control = situation is artificial = lack ecological validity (do not reflect natural behaviour)
- – Lack mundane (everyday) realism
Field experiments
Carried out in real world setting. The researcher still manipulates IV but little control over extraneous variables, but participants don’t know they are taking part in experiment
- + Participants don’t know they are in a study = no demand characteristics
- + Participants behaving naturally = research has higher validity = behaviour reflects real life
- – Loss of control over potential extraneous variables = harder to find causal relationship between IV + DV
- – Harder to replicate – because of lack of control over extraneous variables
Natural VS Quasi experiments
IV cannot be manipulated by researcher (for ethical/practical reasons)
Natural = IV refers to a situation or environmental factor e.g. kind of education system a child has been through
Quasi = when IV is an individual difference e.g. gender, intelligence
- + Can study variables that we would not be able to (ethical/practical reasons)
- – Can’t manipulate the IV = must be cautious about assuming a causal relationship relying on natural variation = no control over potentially important extraneous variables