Experiment types

Question 1

What is a lab experiment?

Answer 1

Conducted in a controlled environment.

• High internal validity because extraneous variables are controlled.
• However investigator/experimenter effects and demand characteristics may reduce internal validity.
• Control increases replicability but reduces external validity.

Question 2

What is a field experiment?

Answer 2

• Conducted in more natural surroundings.
• IV is directly manipulated by the experimenter.
• Possible to control extraneous variables, but more difficult than in lab exp.
• Experimenter effects reduced.
• Demand chracteristics may still be problematic.
• Can draw causal conclusion.
• High ecological validity.
• Avoids some participant effects.

Question 3

What is a natural experiment?

Answer 3

• IV is not directly manipulated.
• Causal conclusions cannot be drawn, as IV not directly manipulated.
• Participants are not randomly allocated to conditions, which can reduce validity.
• Allows research where IV can’t be manipulated for ethical/practical reasons e.g. studying patients with schizophrenia/ privation sufferers.

Question 4

Experimental Design

Answer 4

Different designs of experiments:

• Independent groups - seperate groups for each IV
• Repeated Measures - each P does each IV condition
• Matched Pairs - P’s in each independent group matched with Ps in other goups on key variables e.g. age/IQ