-7-
Unpaired 2 Sample t-Test: Cartoon Data
Signal
in Voxel,
in each
condition,
from 7
subjects
(% change)
Condition
# 1
Condition
# 2
±1 SEM
-2 SEM
+2 SEM
¥ Condition = some way to categorize data (e.g., stimulus type, drug treatment, day of scanning, subject type, É)

¥ SEM = Standard Error of the Mean = standard deviation of sample divided by square root of number of samples
= estimate of uncertainty in sample mean

¥ Unpaired t-test determines if sample means are Òfar apartÓ compared to size of SEM
¥  t statistic is difference of means divided by SEM
one data
sample =
signal from
one subject
in this voxel
in this
condition
¥ Not significantly different!