Net Station Waveform Tools - College of Education & Human ...

Four Cells
To expand on the example given in “Two Cells” on page 185, let us have the subjects
indicate not only if a word has a positive (“good”) or a negative (“bad”) connotation,
but also whether it applies (“yes”) or does not apply (“no”) to themselves. This would
result in four complex categories, each consisting of two traits.
With our word experiment, we would enter “good-no” and “good-yes” into
column a-c, and “bad-no” and “bad-yes” into column b-d, so that the columns and
rows are crossed (“good” and “bad” in each column, and “no” and “yes” in each
row):
Net Station Waveform Tools Technical Manual S-MAN-200-WFTR-001 • December 21, 2006
(no)
(yes)
The tool compares the relationships between the columns, the rows, and the
interaction between the columns and rows (the interaction qualifies the main effects).
The resulting three t-tests are:
(good) (bad)
a b
c d
• a t-test of the mean of cells a and c compared with the mean of cells b and d
(a Column t-test)
• a test of the mean of cells a and b compared with the mean of cells c and d
(a Row t-test)
• a t-test of the difference between cells a and b compared with the difference
between cells c and d (an Interaction t-test)
Because the cells contain compound categories (such as “bad-no,” rather than simply
“bad”), the interaction allows us to separate the traits in the categories. This allows us
to show how a main effect (for example, bad words having a greater medial frontal
negativity) is qualified by the interaction (a greater response of “yes” to bad words).
20: T-test
187