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3.3 Investigating a single independent variable 49

• H1: There is no difference in typing speed when using a QWERTY keyboard, a
1
DVORAK keyboard, or an alphabetically ordered keyboard.
• H2: There is no difference in the time required to locate an item in an online
store between novice users and experienced users.
• H3: There is no difference in the perceived trust toward an online agent among
customers who are from the United States, Russia, China, and Nigeria.

The number of conditions in each experiment is determined by the possible values
of the independent variable. The experiment conducted to investigate hypothesis H1
would involve three conditions: the QWERTY keyboard, the DVORAK keyboard,
and the alphabetically ordered keyboard. The experiment conducted to investigate
hypothesis H2 would involve two conditions: novice users and experienced users.
And the experiment conducted to investigate hypothesis H3 would involve four con-
ditions: customers from the United States, Russia, China, and Nigeria.
Once the conditions are set, we need to determine the number of conditions
to which we would allow each participant to be exposed by selecting either a
between-group design or a within-group design. This is a critical step in experi-
mental design and the decision made has a direct impact on the quality of the data
collected as well as the statistical methods that should be used to analyze the data.

3.3.1 BETWEEN-GROUP DESIGN AND WITHIN-GROUP DESIGN
Between-group design is also called “between-subject design.” In a between-group de-
sign, each participant is only exposed to one experimental condition. The number of
participant groups directly corresponds to the number of experimental conditions. Let
us use the experiment on types of keyboard as an example. As shown in Figure 3.3, three

QWERTY DVORAK Alphabetic
keyboard keyboard keyboard

FIGURE 3.3
Between-group design.

1
Dvorak keyboard is an ergonomic alternative to the commonly used “QWERTY keyboard.” The
design of the Dvorak keyboard emphasizes typist comfort, high productivity, and ease of learning.