Information Technology Reference
In-Depth Information
CHAPTER ELEVEN
Two-Way Within-Subjects Design
11.1 COMBINING TWOWITHIN-SUBJECTS FACTORS
A two-way within-subjects design is one in which the levels of two within-
subjects variables are combined factorially. Recall from Chapter 11 that
within-subjects independent variables can be either time related or not.
There are three possible combinations of types of within-subjects vari-
ables that can be represented in a two-way design: (a) both can be time
independent, (b) one can be time independent and the other time based,
and (c) both can be time based. This latter combination is not often found
in the research literature; the other two are more common, and we provide
illustrations of them here.
Both variables time independent
: Students can be asked to indicate
if short bursts of music are either rock or classical (music variable)
under either silent or noisy conditions (noise variable). In such a
situation, participants would be exposed randomly to the various
combinations of the independent variables. The dependent variable
could be speed of recognition of the music.
One variable time independent and the other variable time dependent
:
Students can be asked to indicate if short bursts of music are either
rock or classical (music variable); these judgments could be made
after they had been awake for either four, twelve, or twenty-four
hours (a time-since-sleep variable). At each level of time since sleep,
the students would be exposed to the two kinds of music in a random
order. The time-since-sleep variable could be operationalized by
either (a) measuring the students over the course of a day first at
four hours, then at twelve hours, and finally at twenty-four hours
after sleep, or (b) measuring the students on one day at one of these
levels (determined randomly among the three), measuring them
on a second day at one of the two remaining levels (determined
randomly), and measuring them on a third day at the one remaining
level of the time-since-sleep variable. The dependent variable could
still be speed of recognition of the music.
287
