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effect on the participants. The other group of seven students answered
the questions in a room painted a bright red (Red Room group); this
color was expected to be more agitating than calming. The dependent
variable was the overall score on the mood questionnaire with higher
scores indicating a more relaxed mood. It was hypothesized that students
answering the questions in the blue room would produce higher scores
than those answering the questions in the red room (i.e., students in the
blue room would indicate more calmness or relaxation than those in the
red room).
3.2.2 THE DESIGN OF THE STUDY
ANOVA is a general statistical technique that we use to compare the
scores in one condition to those of one or more other conditions. It
is useful to distinguish among three classes of ANOVA designs: between-
subjects designs, within-subjects or repeated-measures designs, and mixed
designs. These will be described in detail in Chapters 6-15. For now it is
sufficient for our purposes to note that this example study falls into the
class of between-subjects designs. The defining element of a between-
subjects design is that each participant contributes just one score to the
analysis. Thus, the number of data points we enter into the analysis is
equal to the number of cases in the study.
In the room color study we have fourteen participants, seven in each
group; consequently, we have fourteen pieces of data, seven for each con-
dition. It follows from this arrangement that the levels of the independent
variable are represented by different cases or participants; in this example
some of the students are assigned to the blue room and others are assigned
to the red room.
We can further specify the particular design of our example study. The
between-subjects design that we are using as our example is a one-way
design. In a one-way between-subjects design there is only one independent
variable (the one in one-way signifies this). In the present instance the
independent variable is room color and it has two levels: the room color
is either blue or it is red.
In the ANOVA designs that we cover in this topic, all participants in a
single design are measured on the same dependent variable. In the current
example, we are assessing calmness of mood via scores on a paper-and-
pencil inventory.
3.2.3 THE DATA COLLECTED IN THE STUDY
The data from this hypothetical study are shown in Table 3.1. As can
be seen in the table, participants in the Red Room condition had scores
ranging from 11 to 17 and those in the Blue Room condition had scores
ranging from 16 to 22. There is some overlap between the two distribu-
tions of scores but the means of the two groups are in the direction of the
experimental hypothesis: The mean of participants in the Blue Room con-
dition is higher than that for the Red Room condition. Thus, qualitatively
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