RM- types of experiments

Laboratory experiment

Carried out in a controlled environment

Quasi experiment

Experimenter does not control the independent variable- it is naturally occurring

Ecological Validity

The extent the experiment reflects real life

What laboratory experiment does

Isolates variable to control unwanted variables so we know our variable affects the dependent

Pros of laboratory experiments

High in internal validity- only independent variable manipulated

Dependent variable can be precisely measured

Accurately establishes cause and effect

Highly scientific (observable)

Experimenter can remain detached, reducing risk of researcher bias

Cons of laboratory experiments

Artificial setting means low ecological validity- behaviour may not represent real life setting

Participants likely know they are taking part of an experiment- causing demand characteristics

Field experiment

Carried out in a natural environment, independent variables are controlled by the experimenter, situational variables can sometimes be controlled but largely not

Pros of field experiments

Independent variables can be manipulated

More ecological validity

Some control over extraneous variables

Cons of field experiments

Cause and effect is less reliable

Natural experiment

Experimenter does not control the independent variable as it is naturally occurring (e.g. investigating mental illness)

Pros of natural experiments

Let us research things that cannot be manipulated for ethical or practical reasons

Psychologists can study ‘real’ problems which increases ecological validity

Cons of natural experiments

Cannot display casual relationships as the independent variable is not directly manipulated

Cannot do random allocation which threatens validity

Participants may know they are being studied which lowers internal validity