If two groups in an experiment consist of different individuals then this is an independent measures design. 

The main advantage of an independent measures design is that there is no problem with order effects. 

However, the design also has disadvantages.  The most serious is the potential for error resulting from individual differences between the groups of participants taking part in the different conditions. 

Also if participants are in short supply, then an independent groups design may represent an uneconomic use of those available to participate, since twice as many participants are needed to obtain the same amount of data as would be required in a two-condition repeated measures design.

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Last Updated on 19 November 2009