control over variables

• individual differences

  =randomly allocate ps to each condition (matched pairs or repeated measures design)
• demand characteristics

  deception - single blind technique = p doesnt know the aim
• investigator effects

  =double blind technique - neither ps nor researcher know aim

  =standardised instructions -same instructions given in the same way to avoid bias (video or written)
• situational variables (time,location,temp,noise)


  =try to make them the same in each condition and control them as much as possible