1
Chapter
Introduction to
Statistics
Copyright 2019, 2015, 2012, Pearson Education, Inc.
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Chapter Outline
• 1.1 An Overview of Statistics
• 1.2 Data Classification
• 1.3 Data Collection and Experimental Design
Copyright 2019, 2015, 2012, Pearson Education, Inc.
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Section 1.1
An Overview of Statistics
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Section 1.1 Objectives
• A definition of statistics
• How to distinguish between a population
and a sample and between a parameter and
a statistic
• How to distinguish between descriptive
statistics and inferential statistics
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What is Data?
Data
Consist of information coming from
observations, counts, measurements, or
responses.
• According to a survey, more than 7 in 10
Americans say a nursing career is a
prestigious occupation. (Source: The Harris
Poll)
• “Social media consumes kids today as well,
as more score their first social media
accounts at an average age of 11.4 years old.
” (Source: Influence
Central’s 2016 Digital
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What is Statistics?
Statistics
The science of collecting,
organizing, analyzing,
and interpreting data in
order to make decisions.
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Data Sets
Population
The collection of all
outcomes, responses,
measurements, or counts
that are of interest.
Sample
A subset, or part, of the
population.
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Example: Identifying Data
Sets
In a recent survey, 834 employees in the
United States were asked if they thought there
jobs were highly stressful. Of the 834
respondents, 517 said yes. Identify the
population and the sample. Describe the
sample data set. (Source: CareerCast Job Stress
Report)
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Solution: Identifying Data
Sets
• The population consists of the responses of
all employees in the U.S.
• The sample consists of the responses of the
834 employees in the survey.
• The sample is a subset of
the responses of all
employees in the U.S.
• The data set consists of
517 yes’s and 317 no’s.
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Parameter and Statistic
Parameter
A numerical description of a
population characteristic.
Average age of all people in the
United States
Statistic
A numerical description of a
sample characteristic.
Average age of people from a
sample of three states
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Example: Distinguish Parameter and Statistic
Decide whether each number describes a
population parameter or a sample statistic.
1. A survey of several hundred collegiate
student-athletes in the United States
found that, during the season of their
sport, the average time spent on athletics
by student-athletes is 50 hours per week.
(Source: Penn Schoen Berland)
Solution:
1. Because the average of 50 hours per
week is based on a subset of the
population, it is a sample statistic.
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Example: Distinguish Parameter and Statistic
Decide whether the numerical value describes
a population parameter or a sample statistic.
2. The freshman class at a university has an
average SAT math score of 514.
Solution:
2. Because the average SAT math score
of 514 is based on the entire freshman
class, it is a population parameter.
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Example: Distinguish Parameter and Statistic
Decide whether the numerical value describes
a population parameter or a sample statistic.
3. In a random check of several hundred
retail stores, the Food and Drug
Administration found that 34% of the
stores were not storing fish at the proper
Solution:
temperature.
3. Because 34% is based on a subset of the
population, it is a sample statistic.
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Branches of Statistics
Descriptive
Statistics
Involves
organizing,
summarizing,
and displaying
data.
Inferential
Statistics
Involves using
sample data to
draw conclusions
about a
population.
e.g. Tables, charts,
averages
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Example: Descriptive and
Inferential Statistics
For each study, identify the population and the
sample. Then determine which part of the
study represents the descriptive branch of
statistics. What conclusions might be drawn
from
the study
using
inferential
statistics?
1.
A study
of 2560
U.S.
adults
found that of adults not
using
the Internet, 23% are from
households earning less
than $30,000 annually, as
shown in the figure. (Source:
Pew Research
Center)
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2019, 2015, 2012, Pearson Education, Inc.
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Solution: Descriptive and
Inferential Statistics
Solution:
1. The population consists of the responses of
all U.S. adults, and the sample consists of the
responses of the 2560 U.S. adults in the
study. The descriptive branch of statistics
involves the statement “23% [of U.S. adults
not using the Internet]
are from households earning less
than $30,000 annually.” A possible
inference drawn from the study
is that lower-income households
cannot afford
access to the Internet.
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Example: Descriptive and
Inferential Statistics
For each study, identify the population and the
sample. Then determine which part of the
study represents the descriptive branch of
statistics. What conclusions might be drawn
from the study using inferential statistics?
2. A study of 300 Wall Street analysts found
that the percentage who incorrectly
forecasted high-tech earnings in a recent
year was 44%. (Adapted from Bloomberg
News)
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Solution: Descriptive and
Inferential Statistics
Solution:
2. The population consists of the high-tech
earnings forecasts of all Wall Street analysts,
and the sample consists of the forecasts of
the 300 Wall Street analysts in the study.
The part of this study that represents the
descriptive branch of statistics involves the
statement “the percentage [of Wall Street
analysts] who incorrectly forecasted hightech earnings in a recent year was 44%.” A
possible inference drawn from the study is
that the stock
market is difficult to forecast, 18
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