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SecTIoN 1A Statistics: The Language of Variation 3

The Smelling Parkinson’s activity outlined the steps in the statistical problem-
solving process : (1) Ask questions, (2) collect data, (3) analyze the data, and (4) inter-
1
pret the results. Researchers began by identifying the question to be answered:
“Can Joy Milne smell Parkinson’s disease?” To answer this question, the researchers
designed and carried out an appropriate plan to collect data. The resulting data
consisted of Joy’s 11 correct and 1 incorrect shirt identifications. When analyzing
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the data, researchers had to consider the possibility that Joy was just guessing and
correctly identified 11 of the 12 shirts by chance alone. After careful analysis, the
researchers concluded that Joy Milne could actually smell Parkinson’s disease. To
make the case even stronger, the researchers later discovered that Joy had correctly
identified all 12 shirts. Her one “mistake” was a person who was diagnosed with
Parkinson’s disease a few months later. That’s pretty amazing!
®
In AP Statistics, you will be asked to solve a variety of statistical problems.
Your success will depend on steadily developing skills in four categories: selecting
statistical methods, analyzing data, using probability and simulation, and making sta-
2
tistical arguments. We’ll emphasize both content and skills throughout the book.

SECTION 1A Statistics: The Language

of Variation

LEARNING TARGETS By the end of the section, you should be able to:

• Identify the individuals and variables in a set of • Make and interpret a frequency table or a relative

data, and classify the variables as categorical or frequency table for a distribution of data.
quantitative.

People’s opinions vary on all kinds of issues. Data on physical characteristics
of people, animals, and plants vary from one individual to another. Chance
outcomes — like tosses of a coin or guesses about which shirts were worn by
patients with Parkinson’s disease — vary. Statistics is the language of variation.
This section starts by showing you how to organize and classify data. Then,
you will learn how to represent data in tabular form.
Individuals and Variables

Every year, the U.S. Census Bureau collects data from more than 3.5 million randomly
selected U.S. households as part of the American Community Survey (ACS). The table
displays some data from 10 households included in the ACS in a recent year. 3
People in Time in Response Household Internet
Household Region household dwelling (years) mode income ($) access?
1 South 3 20–29 Phone 272,000 Yes
2 Midwest 3 30 + Internet 54,600 Yes
5 South 1 10–19 Mail 49,900 Yes
6 South 2 2–4 Phone 297,000 Yes
Bruce Leighty/Photodisc/Getty Images 11 Midwest 3 10–19 Internet 133,000 Yes
130,000
5–9
4
Yes
Northeast
Internet
7
82,000
2–4
Internet
3
57,000
Midwest
14
Yes
West
Mail
2–4
36,800
3
Yes
16
Yes
Mail
2
South
17
2–4
80,000
25
No
Mail
1
20–29
Midwest
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