Carryover Effects (2 of 4)
Assume two experimental conditions: A
_{1} and A
_{2}.
Half
the subjects perform in Condition A
_{1} first and
then in A
_{2}; the other subjects perform in Condition
A
_{2} first and then in A
_{1}. The following table of
means shows "symmetric carryover effects."

Condition 
Order 
A_{1} 
A_{2} 
A_{1} given first 
8 

A_{2} given first 

5 



A_{1} given second 
10 

A_{2} given second 

7 
First notice that performance in Condition A
_{1} is three
points better than performance in Condition A
_{2}.
That is, performance was three points higher in A
_{1} when A
_{1} was
first than it was in A
_{2} when A
_{2} was first. The same is
true for performance in a condition when it was performed second.
Now consider the carryover effects by comparing the performance in
Condition A
_{1} when A
_{1} was given first with
performance in Condition A
_{1} when A
_{1} was given
second. The table shows that performance in Condition A
_{1}
was two points better when it was given second (10) than when it was
given first (8). Now, notice that the carryover effect is the same
for Condition A
_{2}: Performance in A
_{2} was two
points better when it was performed second (7) than when it was
performed first (5). Therefore, performing in Condition A
_{1}
prior to performing in Condition A
_{2} raises performance in
Condition A
_{2} by two points. Analogously, performing in
Condition A
_{2} prior to performing in Condition
A
_{1} raises performance in Condition A
_{1} by two
points. The carryover effects are thus symmetric.