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

Overview

Welcome to Module 5. If you are coming from Module 4, you have just learned about correlations by looking at scatter plots and using the Pearson's correlation coefficient.

In this module, we are going to use the t-test statistic to compare the difference between means. Specifically, we are trying to answer the following research question:

Did program participants reduce use of alcohol, tobacco, and other drugs compared to nonparticipants?

To illustrate the t-test, we will look at respondents' use of inhalants. (Note that to fully answer this research question, we would look at changes for all substances contained in the GPRA evaluation instrument.)