Experimental Designs

• Independant Groups; Ppts take part in 1 condition only, each condition has different groups of ppts

  +Lowers order effects, only complete 1 condition, less chance of becoming better/bored

  +Lowers demand characteristics as only 1 condition, less likely to give away the aim

  -Ppt variables may affect the DV due to the separate conditions, lowers internal validity

  -More ppts needed, 2 different groups required to do so
• Repeated Measures; All ppts take part in all conditions of the experiment

  +Ppt variables between ppts removed, increases internal validity

  +Requires fewer ppts as they take part in all conditions, increases population validity

  -Increases demand characteristics, take part in all conditions, may notice clues, help/hinder, lowers internal validity

  -Order effect, take part in more than 1 condition, become bored or better, lowers internal validity
• Matched Pairs; Ppts are matched on important characteristics, each member put in each condition

  +Control the ppt variables of ppt through matching them on key characteristics

  +No order effects, ppts only do 1 condition so they won't get bored or better

  -Time consuming to match ppts through similar traits, large amount of ppts needed

  -Difficult to completely match ppts on characteristics, so ppt variables still have some effect