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

Module Content Objectives Introduction Reported Use of Marijuana Missing Data Analysis of Marijuana Use Subgroup Analysis Standard Deviation What Did Jack Learn From This Analysis? Lessons Learned: What Jack Should Have Asked His Evaluator How Can Jack Use This Statistical Information To Improve His Program? How Can Jack Use This Statistical Information To Promote the Results of His Program? Module 2 Quiz

What Did Jack Learn From This Analysis?

Girls

The standard deviation for the girls at pretest was 2.37, while the standard deviation at posttest was 5.15. This tells us that the girls' marijuana use was greater and varied much more after participating in Jack's program. In other words, the girls' marijuana use was all over the map.

Most of the girls were not using marijuana, some were using occasionally, and some were using quite frequently. Although over half the girls were not using marijuana at posttest, the girls who were using marijuana did so frequently. (One reported smoking 20 times in the last month!) From this information, it appears that the program was not effective in reducing marijuana use among girls.

Boys

The standard deviation for the boys decreased from 3.14 at pretest to 2.55 at posttest. In other words, the boys who were using marijuana frequently were not using as often. Based on this information, it appears that Jack has been successful in decreasing marijuana use among the boys in his program.

Jack was thrilled to discover a success for at least one group of participants (boys). This was a great surprise, because the preliminary evaluator's report said that marijuana use had gone up for all program participants.