Agresti/Franklin Statistics, 1 of 33 Chapter 1 Statistics: The Art and Science of Learning from Data Learn …. What Statistics Is Why Statistics Is Important.

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Chapter 1Statistics: The Art and Science of

Learning from Data

Learn ….

What Statistics Is

Why Statistics Is Important

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Chapter 1

Learn…

How Data is Collected

How Data is Used to Make

Predictions

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Section 1.1

How Can You Investigate using Data?

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Health Study

Does a low-carbohydrate diet result in significant weight loss?

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Market Analysis

Are people more likely to stop at a Starbucks if they’ve seen a recent TV advertisement for their coffee?

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Heart Health

Does regular aspirin intake reduce deaths from heart attacks?

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Cancer Research

Are smokers more likely than non-smokers to develop lung cancer?

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To search for answers to these questions, we…

Design experiments

Conduct surveys

Gather data

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Statistics is the art and science of:

Designing studies Analyzing data Translating data into knowledge and

understanding of the world

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Example from the National Opinion Center at the University of Chicago:

General Social Survey (GSS) provides data about the American public

Survey of about 2000 adult Americans

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Example from GSS: Do you believe in life after death?

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Three Main Aspects of Statistics

Design

Description

Inference

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Design

How to conduct the experiment

How to select the people for the survey

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Description

Summarize the raw data

Present the data in a useful format

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Inference

Make decisions or predictions based on the data.

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Example from GSS: On a typical day, about how many hours do you personally watch television?

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What percentage of the people surveyed reported watching 0 hours of TV a day?

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Example: Harvard Medical School study of Aspirin and Heart attacks

Study participants were divided into two groups• Group 1: assigned to take aspirin

• Group 2: assigned to take a placebo

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Example: Harvard Medical School study of Aspirin and Heart attacks

Results: the percentage of each group that had heart attacks during the study:

0.9% for those taking aspirin 1.7% for those taking placebo

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Example: Harvard Medical School study of Aspirin and Heart attacks

Can you conclude that it is beneficial for people to take aspiring regularly?

Example: Harvard Medical School study of Aspirin and Heart attacks

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Section 1.2

We Learn About Populations Using Samples

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Subjects

The entities that we measure in a study

Subjects could be individuals, schools, countries, days,…

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Population and Sample

Population: All subjects of interest

Sample: Subset of the population for whom we have data

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Example Format

• Picture the Scenario

• Question to Explore

• Think it Through

• Insight

• Practice the concept

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Example: The Sample and the Population for an Exit Poll

In California in 2003, a special election was held to consider whether Governor Gray Davis should be recalled from office.

An exit poll sampled 3160 of the 8 million people who voted.

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What’s the sample and the

population for this exit poll?

The population was the 8 million people who voted in the election.

The sample was the 3160 voters who were interviewed in the exit poll.

Example: The Sample and the Population for an Exit PollExample: The Sample and the Population for an Exit Poll

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Descriptive Statistics

Methods for summarizing data

Summaries usually consist of graphs and numerical summaries of the data

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Types of U.S. Households

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Inference

Methods of making decisions or predictions about a populations based on sample information.

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Parameter and Statistic

A parameter is a numerical summary of the population

A statistic is a numerical summary of a sample taken from the population

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Randomness

Simple Random Sampling: each subject in the population has the same chance of being included in that sample

Randomness is crucial to experimentation

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Variability

Measurements vary from person to person

Measurements vary from sample to sample

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a. To describe whether a sample has more females or males.

b. To reduce a data file to easily understood summaries.

c. To make predictions about populations using sample data.

d. To predict the sample data we will get when we know the population.

Inferential Statistics are used: