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20: T-test
The results are output to a t-file that includes six categories:
• Column t-test
• Column t-test Error
• Row t-test
• Row t-test Error
• Interaction t-test
• Interaction t-test Error
The Column, Row, and Interaction t-test categories contain the t-values for each
channel at each timepoint for each respective comparison; the Column, Row, and
Interaction t-test Error categories show the standard error of the difference for each
channel at each timepoint for each respective comparison. You can view these data by
rolling your cursor over the data (for an example, see Figure 20-3 on page 186).
The formulas for the four-cell t-test are:
for columns
for rows
for interaction
t ∑[ ( ai + ci) – ( bi + di) ] ⁄ n
1 = ----------------------------------------------------------------
S( a+ c)
– ( b+ d)
⁄ ( n)
t ∑[ ( ai + bi) – ( ci + di) ] ⁄ n
2 = ----------------------------------------------------------------
S( a+ b)
– ( c+ d)
⁄ ( n)
t1× 2
∑[ ( ai – bi) – ( ci – di) ] ⁄ n
= ---------------------------------------------------------------
S( a– b)
– ( c– d)
⁄ ( n)
188 Net Station Waveform Tools Technical Manual S-MAN-200-WFTR-001 • December 21, 2006