GFor example:
å Subject 1 - Signal in hippocampus goes from 1000 (baseline) to
1050 (stimulus condition)
å Difference = 50 IRF units
å
å Subject 2 - Signal in hippocampus goes from 500 (baseline) to 525
(stimulus
condition)
å Difference = 25 IRF units
å
GConclusion:
åSubject 1 shows twice as much activation in response to the stimulus condition than does Subject 2 --- WRONG!!
å
åIf ANOVA were run on these difference scores, the change
in baseline from subject to subject would add
variance to the analysis
åWe must control for these differences in baseline across
subjects by somehow normalizing the baseline so
that a reliable comparison between
subjects can be made