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

PREVIEW
Research suggests that romantic background music
increases the likelihood that a woman will give her
phone number to a man she has just met (Guéguen,
Jacob, & Lamy, 2010). The participants in the study
were female undergraduate students, 18–20 years old,
who were recruited to take part in research on product
evaluation. Each woman was taken to a waiting room
with background music playing. For some of the women,
the music was a popular love song and for the others, the
music was a neutral song. After 3 minutes the participant
was moved to another room in which a 20-year-old man
was already waiting. The men were part of the study and
were selected because they previously had been rated as
average in attractiveness. The participant and the confederate
were instructed to eat two cookies, one organic
and one without organic ingredients, and then talk about
the differences between the two for a few minutes. After
5 minutes, the experimenter returned to end the study
and asked the pair to wait alone for a few minutes.
During this time, the man used a scripted line to ask
the woman for her phone number.
You should recognize this study as an example of an
experiment. The researchers manipulated the type of
music to create two treatment conditions and randomly
assigned women to conditions to control extraneous
variables. They recorded whether each woman gave her
number to obtain a set of scores in each treatment and
then compared the two sets of scores.
Table 17.1 shows the structure of this design represented
by a matrix with the independent variable (different
music) determining the rows of the matrix and
the two categories for the dependent variable (yes/no)
determining the columns. The number in each cell of
the matrix is the frequency count showing how many
participants are classified in that category. For example,
of the 44 women who heard the romantic music, there
were 23 (52.3%) who gave their phone numbers. By comparison,
only 12 of the 43 women (27.9%) who heard
the neutral music gave their numbers. The researchers
would like to use these data to support the argument that
romantic background music increases the likelihood that
a woman will give her number to a man she has just met.
Although the Guéguen et al. study involves an independent
variable (the type of music) and a dependent
variable (did she give her number), you should realize
that this study is different from any experiment we have
considered in the past. Specifically, the study does not
produce a numerical score for each participant. Instead,
each participant is simply classified into one of two
categories (yes or no). The data consist of frequencies
or proportions describing how many individuals are in
each category. You should also note that Guéguen et al.
want to use a hypothesis test to evaluate the data. The
null hypothesis would state that the type of background
music has no effect on whether a woman will give her
phone number. The hypothesis test would determine
whether the sample data provide enough evidence to
reject this null hypothesis.
Because there are no numerical scores, it is impossible
to compute a mean or a variance for the sample
data. Therefore, it is impossible to use any of the familiar
hypothesis tests (such as a t test or analysis of variance
(ANOVA) to determine whether there is a significant
difference between the treatment conditions. What is
needed is a new hypothesis testing procedure that can be
used with non-numerical data.
In this chapter we introduce two hypothesis tests
based on the chi-square statistic. Unlike earlier tests
that require numerical scores (X values), the chi-square
tests use sample frequencies and proportions to test
hypothesis about the corresponding population values.
TABLE 17.1
A frequency distribution table
showing the number of participants
who answered either yes or
no when asked for their phone
numbers. One group listened to
romantic music while in a waiting
room and second group listened to
neutral music.
Type of
Music
Gave Phone Number?
Yes No
Romantic 23 21
Neutral 12 31
560