In this chapter, we introduce the ideas of what statistics and data are all about.

Chapter 1Stats Starts Here

Definitions

Statistics is the study of variation that occurs in the real, imperfect world in which we live.

Definitions

Statistics is the study of variation that occurs in the real, imperfect world in which we live.

Descriptive Statistics is about analyzing and summarizing data.

This can be done with charts, graphs and/or numerical analysis.

Definitions

Statistics is the study of variation that occurs in the real, imperfect world in which we live.

Descriptive Statistics is about analyzing and summarizing data.

This can be done with charts, graphs and/or numerical analysis.

Inferential Statistics is about taking the results from analysis of a sample and using them to make inferences about the population from which the sample came.

Definitions

The population is the collection of all individuals/objects about which we’d like to understand or gather information.

A sample is any subset of the population. This is what is actually studied, and from what data is

collected.

Definitions

We will think of data as any collection of numbers, characteristics, images, or other items that provide information about something.

Definitions

We will think of data as any collection of numbers, characteristics, images, or other items that provide information about something.

In a statistical study, the “Five W’s” will be of interest to us:

Who: the sample from which data is collected

What: what data is collected; what variables are recorded

Where

When

Why: what is the goal of the knowledge gained?

Definitions

The characteristics recorded about each individual in the study/sample are variables.

Definitions

The characteristics recorded about each individual in the study/sample are variables.

When a variable answers questions about how observations fall into certain categories, it’s called a categorical or qualitative variable.

Such a variable typically has no units.

Its value is observed, not measured.

Definitions

The characteristics recorded about each individual in the study/sample are variables.

When a variable answers questions about the value of some measurable quantity, it’s called a quantitative variable.

Such a variable typically has units and is measured.

Example 1

For the scenario described below, identify the “W’s”. For each variable, state whether it is categorical or quantitative. If it is quantitative, give the units.

The Gallop Poll conducted a representative telephone survey of 1180 American voters during the first quarter of 2007. Among the reported results were the voter’s region (northwest, south, etc.), age, party affiliation, and whether or not the person voted in the 2006 midterm congressional election.

Example 2

For the scenario described below, identify the “W’s”. For each variable, state whether it is categorical or quantitative. If it is quantitative, give the units.

Business analysts hoping to provide information helpful to American grape growers compiled these data about 20 vineyards: size (acres), number of years in existence, state, varieties of grapes grown, average case price ($), and gross sales ($).