| a | b | c | d | e | f | g | h | i | j | k | l | m |
| n | o | p | q | r | s | t | u | v | w | x | y | z |
ABBA design
This is an example of counterbalancing. When Counterbalancing experimental conditions the first condition (A) can be followed by two trials of the second condition (B) then by one of the first (A). Counterbalancing is used in order to Average out order effects. However if all of the practice effects take place during the first trial it would be safer to run half of the participants with a BAAB sequence.
A more common use of the term is where a half of the participants experience conditions in the order of A then B and the other half experience the conditions as B then A
