Statistics for the Behavioral Sciences by Frederick J. Gravetter, Larry B. Wallnau ISBN 10: 1305504917 ISBN 13: 9781305504912

SECTION 8.1 | The Logic of Hypothesis Testing 227
FIGURE 8.3
From the point of view of the
hypothesis test, the entire population
receives the treatment
and then a sample is selected
from the treated population. In
the actual research study, however,
a sample is selected from
the original population and the
treatment is administered to
the sample. From either perspective,
the result is a treated
sample that represents the
treated population.
Known
original
population
m 5 80
Sample
T
r
e
a
t
m
e
n
t
Unknown
treated
population
m 5 ?
Treated
sample
study from the point of view of the hypothesis test. The original population, before treatment,
is shown on the left-hand side. The unknown population, after treatment, is shown
on the right-hand side. Note that the unknown population is actually hypothetical (the
treatment is never administered to the entire population). Instead, we are asking what
would happen if the treatment were administered to the entire population. The research
study involves selecting a sample from the original population, administering the treatment
to the sample, and then recording scores for the individuals in the treated sample. Notice
that the research study produces a treated sample. Although this sample was obtained indirectly,
it is equivalent to a sample that is obtained directly from the unknown treated population.
The hypothesis test uses the treated sample on the right-hand side of Figure 8.3 to
evaluate a hypothesis about the unknown treated population on the right side of the figure.
A hypothesis test is a formalized procedure that follows a standard series of operations.
In this way, researchers have a standardized method for evaluating the results of
their research studies. Other researchers will recognize and understand exactly how the
data were evaluated and how conclusions were reached. To emphasize the formal structure
of a hypothesis test, we will present hypothesis testing as a four-step process that is used
throughout the rest of the book. The following example provides a concrete foundation for
introducing the hypothesis-testing procedure.
EXAMPLE 8.1
Previous research indicates that men rate women as being more attractive when they are
wearing red (Elliot & Niesta, 2008). Based on these results, Guéguen and Jacob (2012)
reasoned that the same phenomenon might influence the way that men react to waitresses
wearing red. In their study, waitresses in five different restaurants wore the same T-shirt
in six different colors (red, blue, green, yellow, black, and white) on different days during
a six-week period. Except for the T-shirts, the waitresses were instructed to act normally
and to record each customer’s gender and how much was left as a tip. The results show that
male customers gave significantly bigger tips to waitresses wearing red but that color had
no effect on tipping for female customers.
A researcher decided to test this result by repeating the basic study at a local restaurant.
Waitresses (and waiters) at the restaurant routinely wear white shirts with black pants
and restaurant records indicate that the waitress’ tips from male customers average μ =
15.8 percent with a standard deviation of σ = 2.4 percentage points. The distribution of tip