Wading Through the Data Swamp:
Program Evaluation 201

Module 1: Descriptive Statistics in Evaluation - Page 9 of 21

Research Question #1

Let's start with the first evaluation question:

  1. Did program participants reduce use of alcohol, tobacco, and other drugs compared to nonparticipants?

Program participants were asked about their marijuana use and alcohol use in questions 1 and 2 of the GPRA Youth Survey (12 years and over), Drug and Alcohol use section.

A persons's finger with a string tied around it. - FYI

In this tutorial we are only looking at the frequency of drug use as opposed to the amount consumed. There are pros and cons associated with either approach. To learn more read Determining Level of Alcohol and Drug Use.

Let's look at what the kids told us about their marijuana use before the program started.

According to the evaluator's report, the kids' average marijuana and alcohol use were about the same, 1 to 2 days in the past month (1.7 and 1.64, to be exact). These figures were fairly consistent with some of the national data on middle-school students that Jack had read about.

A red flag with the word warning written on it.

What the Evaluator Left Out

These averages, or means, masked great differences in the kids' alcohol and marijuana use. This fact had an impact on the interpretation of the evaluation results.

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