Transcript 1.1 Statistics Basics

Copyright © 2008 Pearson Education, Inc.
Chapter 1
The Nature of Statistics
Section 1.1
Statistics Basics
Slide 1-2
Introduction
What is Statistics?
A branch of mathematics devoted to the collection,
description, analysis and interpretation of data.
The science of conducting studies to collect,
organize, summarize, analyze, and draw
conclusions from data.
In what occupations might we use
statistics?
Education: Which method of teaching is best
the old or the new?
Sports: Number of hits a baseball player gets
in one season.
Public Health: Number of residents that
contracted a new strain of flu.
Slide 1-3
What are the two branches of Statistics?
Descriptive Statistics
Descriptive Statistics consists of methods for organizing and
summarizing information.
Descriptive statistics includes the construction of graphs, charts,
and tables and the calculation of various descriptive measures such as
averages, measures of variation, and percentiles.
Consists of the collection, organization, summarization, and
presentation of data.
The statistician tries to describe a situation.
The goal is simply to describe a set of data that has been collected,
whether the data represents an entire population or a sample.
(Chapters 2 and 3)
Slide 1-4
Descriptive Statistics
The 1948 Baseball Season In 1948, the Washington
Senators played 153 games, winning 56 and losing 97. They
finished seventh in the American League and were led in
hitting by Bud Stewart, whose batting average was .279
Slide 1-5
Inferential Statistics
Inferential statistics: consists of methods for drawing and
measuring the reliability of conclusions about a population
based on information obtained from a sample of the
Population.
Statisticians analyze the information obtained from a
sample of the voting population to make inferences
(draw conclusions) about the preferences of the entire
voting population. Inferential statistics provides methods
for drawing such conclusions.
Slide 1-6
Inferential Statistics
consists of generalizing from samples to populations,
performing estimations hypothesis testing, determining
relationships among variables, and making predictions.
The statistician tries to make conclusions from samples
and populations.
The goal is to reach a conclusion about a population based
only on knowledge obtained by studying a sample drawn
from that population.
Slide 1-7
Classifying Statistical Studies
In each of these statements, tell whether descriptive or
inferential statistics have been used.
Inferential – making predictions
Descriptive – values that can be counted
• In the year 2010, 148 million Americans will be enrolled in
an HMO (Source: USA TODAY)
Inferential
• Nine out of ten on-the-job fatalities are men. (Source:
USA TODAY Weekend)
Descriptive
• Expenditures for the cable industry were $5.66 billion in
1996 (Source: USA TODAY)
Descriptive
Slide 1-8
Classifying Statistical Studies
• The median household income for people aged 25 – 34 is $35,888
(Source: USA TODAY)
Descriptive
• Allergy therapy makes bees go away (Source: Prevention)
Inferential
• Drinking decaffeinated coffee can raise cholesterol levels by 7%
(Source: American Heart Association)
Inferential
• The national average annual medicine expenditure per
person is $1052 (Source: The Greensburg Tribune review)
Descriptive
• Experts say that mortgage rates may soon hit bottom
(Source: USA TODAY)
Inferential
Slide 1-9
Population and Sample
Political polling provides an example of inferential
statistics.
Interviewing everyone of voting age in the United States on
their voting preferences would be expensive and
unrealistic.
Statisticians who want to gauge the sentiment of the entire
population of U.S. voters can afford to interview only a
carefully chosen group of a few thousand voters. This
group is called a sample of the population.
Slide 1-10
Population
Population: The collection of all individuals or items under
consideration in a statistical study.
When a statistical study is done (meaning data is collected)
the set of all objects being studied is called the population.
The Population then consists of all the subject (human or
otherwise) that are being studied.
Slide 1-11
Sample
Sample: That part of the population from which information
is obtained.
In a statistical study the population might be small and
easily accessible. However, populations are often very large
and, in some cases, theoretical. In such instances, the
population is not going to be easily accessible. Here,
statisticians have to be content with studying a sample
drawn from the population.
Population
Sample
Slide 1-12
Figure 1.1
Slide 1-13
Sample:
If a statistician must work with a sample, it is important
how the sample is selected. The most desirable
characteristic of a sample is that it be representative of
the population from which it is drawn.
Is a subset
or part of a samples
population
. In a
other words,
However, selecting
representative
from
a group of
selected
from
a population.
population is aisscience
insubjects
itself and
is not
a topic
covered in
an elementary statistics course.
We should, however, mention a few of the basic concepts of
sampling theory. For example: random sample and
stratified random sample.
Slide 1-14
What are the two types of studies?

Observational study
Researchers observe characteristics and take measurements.
They merely observes what is happening or what has happened in the
past and tries to draw conclusions based on these observations.
Reveals only association

Designed Experiment
Researchers impose treatments and controls and then observe
characteristics and take measurements.
They manipulates one of the variables and tries to determine how the
manipulation influences other variables.
Helps establish causation
Slide 1-15
Obervational Studies and Designed Experiments
Identify each study as being either observational or experimental.
Observational – researchers observe characteristics and take
measurements.
Designed Experiment – researchers impose treatments and controls and
then observe characteristics and take measurements.
--------------------------------------------------------------------------Subjects are randomly assigned to two groups, and one group was given
a herb and the other group a placebo. After 6 months, the number of
respiratory tract infections each group had were compared.
Designed Experiment
A research stood at a busy intersection to see if the color of the
automobile that a person drives is related to running red lights.
Observational Study
Slide 1-16
Obervational Studies and Designed Experiments
A researcher finds that people that are more hostile have higher total
cholesterol levels than those who are less hostile.
Observational
Subjects are randomly assigned to four groups. Each group is placed on
one of four special diets – a low fat diet, a high fish diet, a combination
of low fat and high fish, and a regular diet. After 6 months, the blood
pressure of these groups are compared to see if diet has any effect on
blood pressure.
Experimental
Slide 1-17
Computers and Calculators

In the past, statistical
calculations were done with
pencil and paper. However,
with the advent of calculators,
numerical computations
became easier.
Slide 1-18
Statistical Packages

Microsoft Excel, MINITAB, the TI-83 and
TI-84 graphing calculator can be used to
perform statistical computations.

Students should realize that the computer and
calculator merely give numerical answers and
save time and effort of doing calculations by
hand. You still have to understand and
interpret the statistical concept.
Slide 1-19
Summary

The two major areas of statistics are
descriptive and inferential.

When the populations to be studied are large,
statisticians use subgroups called
samples.

The two basic types of statistical studies are
observational and designed experiment.
Slide 1-20
Conclusion
The applications of statistics are many and
varied. People encounter them in everyday life,
such as in reading newspapers or magazines,
listening to the radio, surfing the Internet, or
watching television.
Slide 1-21
HOMEWORK – CHAPTER 1.1
Pages 9-11
1, 2, 5, 6, 7, 9, 10, 12, 14, 20, and 23
Slide 1-22