On-Line Ordering System

Chapter 1: Introduction

WHAT ARE STATISTICS?

METHODS FOR ORGANIZING, SUMMARIZING, PRESENTING, & INTERPRETING INFORMATION (DATA)

□ Statistics “bring order to chaos”—condense large amounts

of information into smaller understandable units

□ Vocabulary & symbols for communicating about data

□ How to make “judgments (about data) under uncertainty”

□ A tool box

How do you know which tool to use?

(1) What do you want to know?

(2) What type of data do you have?

BRANCHES OF STATISTICS

1. DESCRIPTIVE STATISTICS

Tools for summarizing, organizing & simplifying data

• Tables & Graphs

• Measures of Central Tendency

• Measures of Variability

Examples:

• Average rainfall in Oxford last year

• Number of car thefts in Cincinnati last semester

• Percentage of seniors in this class

2. Inferential Statistics

Data from sample used to draw inferences about a population

Tools for generalizing beyond actual observations

Generalize from a sample to a population

Population

• The entire collection of events of interest

• E.g., collection of people you want to understand

• Doesn’t necessarily mean “big” but often is

Sample

• Subset of events selected from a population

• Intended to represent the population

Why not just collect data from the whole population?

Sometimes impractical, often impossible!

If we cannot measure everyone in the population, does that mean we cannot study populations or make any conclusions about them?

NO!

Data from a sample can tell us something about a population

Symbols and Terminology

Parameter = Values describing POPULATIONS

Greek letters ( ( (2 ( (

Statistics = Values describing SAMPLES

English letters ( [pic] s2 s r

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