Exam 1 Review
Has the percentage of young girls drinking milk changed over time? The
following table is consistent with the results from “Beverage Choices of Young
Females: Changes and Impact on Nutrient Intakes” (Shanthy A. Bowman,
Journal of the American Dietetic Association, 102 (9), pp. 1234 – 1239:
Nationwide Food Survey Years
Drinks Fluid Milk
Yes
No
Total
1987 - 1988
354
226
580
1989 - 1991
502
335
837
1994 - 1996
366
366
732
Total
1222
927
2149
1. Find the following
a. What percent of young girls reported that they drink milk?
(1222 ÷ 2149)100 = 56.86%
b. What percent of the young girls were in the 1989 – 1991 survey?
(837 ÷ 2149)100 = 38.94%
c. What percent of the young girls who reported that they drink milk were
in the 1989 – 1991 survey?
(502 ÷ 1222)100 = 41.08%
d. What percent of the young girls in the 1989 – 1991 reported that they
drink milk?
(502 ÷ 837)100 = 59.97%
2. What is the marginal distribution of milk consumption?
Yes: (1222 ÷ 2149)100 = 56.86%
No: (927 ÷ 2149)100 = 43.13%
3. Do you think that milk consumption by young girls is independent of the
nationwide survey year? Use statistics to justify your reasoning.
Of all young girls surveyed, 56.9% reported drinking milk, but 60% of the
young girls reported drinking milk in the 1989-1991 survey. Since these
percentages differ, milk consumption and year are not independent.
4. Sketch a stem and leaf for this data: 49, 67, 38, 55, 62, 54, 36, 41, 56, 43, 49,
75, 44, 60, 48, 52, 48, 53, 59, 32.
Firs put them in ascending order:
32 36 38 41 43 44 48 48 49 49 52 53 54 55 56 59 60 62 67 75
7
6
5
4
3
5
0
2
1
2
2
3
3
6
7
4 5 6 9
4 8 8 9 9
8
5. One of the reasons that the Monitoring the Future (MTF) project was started
was “to study the changes in the beliefs, attitudes, and behavior of young
people in the United States.” Data are collected from 8th, 10th, and 12th
graders each year. To get a representative nationwide sample, surveys are
given to a randomly selected group of students. In Spring 2004, students
were asked about alcohol, illegal drug, and cigarette use. Describe the W’s. If
the information is not given, state that it is not specified.
 Who: 8th, 10th, and 12th graders (all categorical variables)

What: alcohol, illegal drug, and cigarette use

When: Spring 2004

Where: United States

How: Survey

Why: “to study changes in the beliefs, attitudes, and behavior of
young people in the United States.”
6. The students in a biology class kept a record of the height (in centimeters) of
plants for a class experiments: 49, 67, 38, 55, 62, 54, 36, 41, 56, 43, 48, 75,
44, 60, 48, 52, 48, 53, 59, 32. Find the:
32 36 38 41 43 44 48 48 48 49 52 53 54 55 56 59 60 62 67 75
a) mean : (32 + 36 +…+ 75) ÷ 20 = 1020 ÷ 20 =51
b) median : (49 + 52) ÷ 2 = 50.5
c) Q1: (43 +44) ÷ 2 = 43.5
d) Q3: (56 +59) ÷2 = 57.5
e) IQR: 57.5 – 43.5 = 14
f) Range: 75 – 32 = 43
g) Standard deviation:
32 36 38 41 43 44 48 48 48 49 52 53 54 55 56 59 60 62 67 75
Y Values
32
36
38
41
43
44
48
48
48
49
52
53
54
55
56
59
60
62
67
75
Deviations (y – Ў)
32 – 51 = -19
36 – 51 = -15
-13
-10
-8
-7
-3
-3
-3
-2
1
2
3
4
5
8
9
11
16
24
Squared Deviations
361
225
169
100
64
49
9
9
9
4
1
4
9
16
25
64
81
121
256
576
S2 = (361 + 225 + …+ 576) ÷ (20 – 1) =113.263
S = √113.263 = 10.64
7. Here is a histogram displaying the amount of time watching television a week
for a group of college students. Describe the time distribution. Make sure to
comment on the shape, center, and spread.
The histogram of amount of time spent watching TV is unimodal and skewed to
the right. The median time spent watching TV is around 8 hours. The data is very
spread with people reporting watching TV between 0 and 30 hours with two
outliers around 40 and 60.
8. This box plot displays the amount of time college students spend studying (in
hours) a week. Write a few sentences describing the amount of study time for
both males and females.
The median time spent studying for males and females are about the same,
between 7 and 8 hours. Females have a larger range of time spent
studying; 28 compared to 18. There is one outlier at 40 hours for males.
The distribution for males appears to be symmetric where the distribution
for females is skewed to the right.
9. Using the table below create a bar chart.
Goals of Thrasher Hockey Players
Player
Ilya Kovalchuk
Todd White
Vyacheslav Kozlov
Bryan Little
Colby Armstrong
Goals
20
14
16
21
13
Goals
25
20
15
10
5
0
Kovalchuk
White
Kozlov
Little
Armstrong
10. Create a pie chart using the table below.
The percentage of high school students who drank alcohol (more than a few
sips) for the first time before the age of 13; the frequency of having had their first
drink before 13 is (according to the 2005 Youth Risk Behavior Surveillance
Survey (YRBSS) conducted by the Centers for Disease Control and Prevention):
Grade
Percentage
12th
19.3
11th
20.5
10th
26.2
9th
33.9
Percentage of students who drank before age 13
19%
34%
12th
11th
10th
9th
21%
26%
11. The data below show the number of shoplifters caught at Lenox mall each
week for 6 months. Create a dotplot of these data
2
4
6
3
4
5
3
2
5
3
0
2
1
5
5
1
3
3
4
4
0
1
2
3
4
5
6