Variables

Situational Variables

• type of extraneous variable

• any feature of the experimental situation that may affect the DV

• e.g. temp, time of day

Participant Variable

• type of extraneous variable

• any individual differences between participants that may affect the DV

• e.g. IQ, gender, age

Investigator Effects

• type of extraneous variable

• any effect of the investigator’s behaviour conscious or unconscious on the DV

• e.g. being nicer or lack of standardisation

Demand Characteristics

• type of extraneous variable

• any cue from the researcher or situation that may reveal the aim/purpose of the investigation leading to a change in behaviour to please or sabotage

• screw you please you effect

Order Effects

• when positioning order of the conditions influences the outcome

• e.g. practice, fatigue

Controlling Extraneous Variables

• randomisation

• standardisation

• random allocation

• counterbalancing

Randomisation

• controls investigator effects

• use chance when designing materials

• use chance when deciding the order of conditions

• reduces researcher’s unconscious biases

Standardisation

• controls investigator effects and situational variables

• all participants are ensured to receive the same experience by using the same formalised procedures and instructions for all participants

Random Allocation

• controls participant variables

• using a random method to decide which participant goes into which condition

Counterbalancing

• controls order effects

• used in a repeated measures design

• half the participants experience the conditions in one order and the other half experience it in the opposite order