CONTENTS

Table of Contents
Introduction

1. Descriptive Statistics in Evaluation
2. Subgroup Analysis
3. Variable - Are They Related?
4. Correlation
5. The t-Test of Difference Between Means

Supplements
Resources
Glossary

Wading Through the Data Swamp:
Program Evaluation 201

Contingency Tables

To determine chi-square, we need to set up a contingency table. A contingency table shows whether the likelihood of being in a category (such as marijuana user) is "contingent on" being in another category (such as the comparison group). This helps show whether a program makes a difference.

A contingency table presents the number and proportion of people falling into two or more categories on two or more nominal-level variables. In our case, we will be comparing two variables (drug use and program participation). Therefore, we will be looking at a 2x2 table.

A 2x2 table is the simplest kind of contingency table. Contingency tables can become much more complex, comparing several different levels of variables. Tables can be 2x4, 3x3, and so on.

Examples:

• 2x2 table
• 2x3 table
• 3x3 table
• 2x5 table

2x4? 3x3? Feel like you're in a lumber yard? It's not as confusing as it seems. Come, I'll walk you through the process.