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

Subgroup Analysis

Subgroup analysis is simply subdividing the data into different categories or subgroups, based on demographics or other important characteristics. For example, subgroups can be based on gender, ethnicity, race, or income. The purpose is to compare the performance of different groups.

Subgroup analysis may help Jack paint a more accurate picture regarding the marijuana use of the kids in his program. We may be able to see specifically which group is using marijuana more often or if there is no difference between groups.

Let's help Jack plot the data in different ways. We'll start with an easy one by comparing boys and girls in the program using demographic information collected in the GPRA survey.

Reported Use of Marijuana

Kid #	Pretest	Posttest

We calculated the means for each group and here is what the results look like.

It looks like the program may have had very different effects for boys and girls, and these effects tended to cancel out in the overall means.