Chapter 1
1.1 The entire student body of your college or university
would be considered a population under any circum-
stances in which you want to generalize onlyto the stu-
dent body of your school.
1.3 The students of your college or university are a nonran-
dom sample of U.S. students, for example, because not
all U.S. students have an equal chance of being included
in the sample.
1.5 Independent variables: first-grade students who attended
kindergarten versus those who did not; seniors, masters,
submasters, and juniors as categories of marathon run-
ners. Dependent variables: social-adjustment scores
assigned by first-grade teachers; time to run 26.2 miles.
1.7 Continuous variables: length of gestation; typing speed
in words minute; and number of books in the library
collection.
1.9 The planners of a marathon race would like to know the
average times of senior, master, submaster, and junior
runners so they can plan accordingly.
1.11 (a) The number of Brown University students in an
October 1984 referendum voting for, and the num-
ber voting against, the university’s stockpiling sui-
cide pills in case of nuclear disaster.
(b) The number of students in a small Midwestern col-
lege who are white, African-American, Hispanic-
American, Asian, or other.
(c) One year after an experimental program to treat
alcoholism, the number of participants who are
“still on the wagon,” “drinking without having
sought treatment,” or “again under treatment.”
1.13 Children’s scores in an elementary school could be
reported numerically (a measurement variable), or the stu-
dents could be categorized as Bluebirds (Rating .90),
Robins (Rating 570 2 90), or Cardinals (Rating ,70).
1.15 For adults of a given height and gender, weight is a
ratio scale of body weight, but it is at best an ordinal
scale of physical health.
1.17 Speed is probably a much better index of motivation
than of learning.
1.19 (a) The final grade point average for low-achieving stu-
dents taking courses that interest them could be
compared with the averages of low-achieving stu-
dents taking courses that do not interest them. (b)
The frequency of sexual intercourse could be com-
pared for happily versus unhappily married couples.
1.21 An interesting study of the health effects of smoking in
China can be found at http://www.berkeley.edu/news/
media/releases/2005/09/04_smoking.shtml.
Chapter 2
2.1 (b) Unimodal and positively skewed.
2.3 The problem with making a stem-and-leaf display of
the data in Exercise 2.1 is that almost all of the values
>fall on only two leaves if we use the usual tens’ digits
for stems. And things are not much better even if we
double the number of stems.
2.5 There is no specific answer other than a graph.
2.7 There is no specific answer.
2.9 The first quartile for males is approximately 77, whereas
for females it is about 80. The third quartiles are nearly
equal for males and females, with a value of 87.
2.11 The shape of the distribution of number of movies at-
tended per month for the next 200 people you met
would be positively skewed, with a peak at 0 movies per
month and a sharp dropoff to essentially the baseline by
about 5 movies per month.
2.13 This is a stem-and-leaf display.
2.15 (a) Y 15 9, Y 1052
(b)
2.17 (a)(b)
(c)
(d) The units of measurement were squared musicality
scores in part (b) and musicality scores in part (c).2.19 (a)(b)(c)(d)2.21 The results in Exercise 2.20 support the sequential
processing hypothesis.
2.23 The data are not likely to be independent observations
because the subject is probably learning the task over
the early trials, and later getting tired as the task pro-
gresses. Thus responses closer in time are more likely to
be similar than responses further away in time.
2.25 The amount of shock that a subject delivers to a white
participant does not depend upon whether or not that
subject has been insulted by the experimenter. On the
other hand, black participants do suffer when the exper-
imenter insults the subject.
2.27 This question asks for a graphic.
2.29 One way to look at these data is to plot the percentage of
households headed by women and the family size sepa-
rately against years. There has been a dramatic increase
in the percentage of households headed by women over(gX)^2 = 772 = 5929gX^2 = 1021821... 172 = 657CgX=3(77)= 231= 231gCX=g 3 X=3(10) 1 3(8) 1... 1 3(7)gXgY=(77)(57)= 4389gXY=10(9) 1 3(8) 1... 1 3(7)= 460gX 1 gY= 77157 = 1341... 1 (7 1 2)= 134g(X 1 Y)=(10 1 9) 1 (8 3 9)1 5.789=2.406gY^22(gY)^2
N
N 21
=3772
3249
10
9
=5.789gY^2 = 92192... 22 = 377(gY)^2 =(9 191... 1 2)^2 = 3249gY= 9191... 12 = 57736 Answers