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

Introduction

• Types of Evaluation
• Data Collection Methods
• Reasons for Conducting an Evaluation

Module 1

• Cool After School Program
• Research Questions
• Research Designs
• Threats to Internal Validity
• Threats to External Validity
• Youth Survey (12 years and over)
• Validity and Reliability
• Determining Level of Drug and Alcohol Use
• Distributions
• Full Checklist of Information to Ask an Evaluator

Module 2

• Cool After School Program
• Full Checklist of Information to Ask an Evaluator

Module 3

• Outcomes
• Contingency Table Examples
• Critical Values of Chi-Square
• Full Checklist of Information to Ask an Evaluator

Module 4

• Cool After School Program
• Full Checklist of Information to Ask an Evaluator

Module 5

• All Substances Contained in the GPRA Evaluation Instrument
• Youth Survey (12 years and over)
• Cool After School Program

Paired sample t-Test for participant pre- and posttests

• Step 1: State null hypothesis
• Step 2: Choose a significance level
• Step 3: Subtract the pretest scores from the posttest scores and add the results.
• Step 4: Calculate the mean for the sum of the differences between posttest scores and pretest scores.
• Step 5: Square the sum of the X values. Then divide by the n value.
• Step 6: Square the differences between posttest scores and pretest scores and add the results.
• Step 7: Complete the sum of squares (SS) calculation.
• Step 8: Divide the sum of squares by the degrees of freedom to get the variance - (S2)
• Step 9: Take the square root of the variance divided by n.
• Step 10: Use the t-Test formula: Divide the mean of X from step 4 by the square root of the variance from step 8 divided by n.
• Step 11: Compare the calculated t-value with the critical t-value found in the table.

• Critical t-value Table

Independent Samples t-Test for Pretest Data

• Step 1: State null hypothesis
• Step 2: Choose a significance level
• Step 3: Determine the difference in means between the two groups
• Step 4: Sum the scores of the pretest for both groups
• Step 5: Square the sum of the scores for both groups
• Step 6: Square each person's score for both groups and sum the squared scores
• Step 7: Complete the sum of squares (SS) calculation
• Step 8: Calculate the degrees of freedom
• Step 9: Calculate the combined variance
• Step 10: Use the t-Test formula
• Step 11: Compare the calculated t-value with the critical t-value found in the table

Independent Samples t-Test for Posttest Data

• Step 1: State null hypothesis
• Step 2: Choose a significance level
• Step 3: Determine the difference in means between the two groups
• Step 4: Sum the scores of the pretest for both groups
• Step 5: Square the sum of the scores for both groups
• Step 6: Square each person's score for both groups and sum the squared scores
• Step 7: Complete the sum of squares (SS) calculation
• Step 8: Calculate the degrees of freedom
• Step 9: Calculate the combined variance
• Step 10: Use the t-Test formula
• Step 11: Compare the calculated t-value with the critical t-value found in the table