How to improve internal validity (x9)
1) Pilot study - find and control for EVs which may affect DV
2) High levels of control - strong cause and effect relationship
3) Ensure ppts do not know the aim of the study - prevents them showing demand characteristics
7) Train researchers to treat ppts equally/use a neutral tone and have an unbiased interpretation of behaviour
8) Standardised procedure - no ppts have an unfair advantage