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 Posttest Data

Step 6: Square each score for both groups and sum the squared scores.

The first task is to square each person's posttest score. For example, participant 1 had a pretest score of 4 . The square of 4 is 16. comparison group member 1 had a posttest score of 3. The square of 3 is 9. Once you have the squares of all the scores for each group, you add them up for each group.

Square of Posttest Scores and Sum of Squared Scores

Participants			Comparison
kid #	Score	Score2	Kid #	Score	Score2

The sum of the squared scores for the participant group is 558. The sum of the squared scores for the comparison group is 1,157. The sum of the squared scores is represented by the formula (scores)². These numbers will be used in step 7, the sum of squares calculation.