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

The t-Test of Differences Between Means:
Independent Samples t-Test for Pretest Data

Step 1: State Null hypothesis

Our null hypothesis (represented as H₀) reads:

H₀ = The mean score for inhalant use for participants is not different from the mean score for inhalant use for the comparison group.
OR
H₀ = The mean difference between the two groups is zero ("null").
OR
H₀ = There is no difference between the means of the two tests. The symbolic representation is H₀ = µ1 - µ2 = 0.

The research hypothesis (represented as H₁) reads:

H₁ = The mean score of inhalant use for participants is different from the mean score of inhalant use for the comparison group.
OR
H₁ = The mean difference between the two is not zero.
OR
H₁ = There is a difference between the means of the two groups. The symbolic representation is H₁ = µ1 - µ2 not equal to 0.