After drinking 300ml of monster ppts will say more words in the next 5 minutes than ppts who drink 300ml of water
What is an extraneous variable?
Any variable other than the IV that may effect the DV. They do not vary systematically with the IV and cannot always be controlled. E.g. weather
Confounding variable
Any variable that may have affected the DV (other than IV) therefore we cannot be sure of the true source of changes to the DV. They vary systematically with IV
Investigator effects
Any effect of the investigators conscious/unconscious behaviour on the research outcome. Can include the design of study/selection and interaction of ppts
Randomisation
The use of chance in order to control for the effects of bias when designing materials and deciding the order of conditions
Standardisation
Using exactly the same formalised procedures and instructions for all ppts in a research study
