Experimental Designs

: each ppt takes part in every condition

Advantage:

+ No individual differences between ppts in different conditions

Disadvantage:

- Risk of order effects, i.e. practice effect - performance might be better in the second condition because the ppts know what to do

*The main way order effects are dealt with is using counterbalancing - Alternating the order in which ppts perform in different conditions of an experiment

: ppts are allocated to two (or more) groups, and then take part in different conditions of the experiment

Advantage:

+ No order effects (because ppts only take part in one condition, depending what group they're in) 

Disadvantages:

- More time consuming (as more ppts are needed)

- More expensive (if ppts get paid)

- Differences between ppts in the groups may affect results - e.g. ppts in Group A may have better memory than ppts in Group B) - these are known as extraneous variables

*These differences can be avoided by randomly allocating ppts to groups

: pairs of ppts are matched in terms of characteristics such as age and IQ etc.

Advantages:

+ Lower risk of demand characteristics 

+ No order effects (same procedure as Independent Groups)

Disadvantages:

- Matching pairs of ppts may be time-consuming and difficult

- Large number of potential ppts needed to achieve matching 

- Not possible to control all ppt variables

* In order to control ppt variables, conduct a pilot study to consider key variables that might be important when matching