Sociology 302

Introduction

Dependent VariableYour “Topic”

What You Want to Change

Independent Variable 1Your “Explanation”

The Cause of Change

Independent Variable 2Your “Explanation”

The Cause of Change

This diagram represents a theory: A set of empirically falsifiable statements about reality. •The dependent variable is the behavior, attitude, or condition about society that you want to change.•The independent variables are potential explanations of the dependent variable. •The arrows represent hypotheses, or statements about reality.

Rate of Juvenile Delinquency

Quality of Parenting

Quality of theNeighborhood

Example

•Dependent variable: Rate of juvenile delinquency.•Independent variables: quality of parenting, quality of the neighborhood. •Hypothesis 1: The lower the quality of parenting, the greater the rate of juvenile delinquency.•Hypothesis 2: The lower the quality of the neighborhood, the greater the rate of juvenile delinquency.

Measurement

To test an hypothesis, we need to measure each of the variables in our hypothesis.

Example: The lower the quality of the neighborhood the greater the rate of juvenile delinquency.

Possible measures of the “quality of a neighborhood”:1.Define “neighborhood.” Example: a census block.2.Devise measures of quality. Examples: income, single parent families, rates of domestic violence, unemployment rate, trash in the streets, housing conditions.3.Assess validity: Do the measures above actually measure “quality of the neighborhood?” Do we agree that these measures are reasonable ones?4.Assess reliability: Are the measures consistent? Do they yield the same results in repeated trials, assuming what we are measuring stays the same.

Quality of theNeighborhood

Quality of theNeighborhood

Measurement

Face and Content ValidityDo the items we are using to measure “quality of the neighborhood” measure what we intend to measure (i.e., quality of neighborhood).

Approach: Community of ScholarsDo other scientists agree with us that the items we listed on the previous slide measure “quality of the neighborhood?”

Quality of theNeighborhood

Measurement

Construct ValidityDo the items we are using to measure “quality of the neighborhood” measure just one thing (i.e., quality of neighborhood).

Approach: Factor AnalysisThis procedure determines if each of our items we use to measure “quality of the neighborhood” measures the same thing?

For example, using the items we listed above, factor analysis might reveal that we are measuring “one thing.” Or, it might reveal that we are measuring three things: Economic quality (income, unemployment rate), Family quality (domestic violence, single parents), and Social quality (housing conditions, trash in the streets).

Data Collection

Research Design•Experiments•Surveys•Cross-sectional, longitudinal•Interviews•Focus groups•Ethnographies•Content analysis

Question Design•Loaded questions•Double-barreled questions•Etc.

Sampling•Convenience•Simple random•Stratified•Cluster

Causality (and Measurement)

Regression Analysis

1.To what extent does our theory explain what we want it to explain (i.e., to what extent are neighborhood quality and parenting related to rates of juvenile delinquency). The answer to this question is the coefficient of reproduction/determination (R-square). The R-square is our “grade,” how well we performed.”

2.How important is each of the independent variables in explaining what we want it to explain? The answer to this question is the standardized estimate (also: regression coefficient, or beta). The larger the beta, the more return on investment.

Other Type of Analysis

Crosstabs (i.e., contingency tables), ANOVA, correlations.

Making the World a Better Place to Be

How good is our theory?

To make the world a better place to be, we have to be able to explain it. The R-square value will let us know how well we explained it.

If we explained our dependent variable sufficiently, then each of the standardized beta coefficients will let us know which of the independent variables is the most important, and where to place the emphasis of our limited resources.

In the hypothetical example depicted on the next page, our R-square is very good (R-square varies from 0 to 1, with the closer to 1 meaning the better the explanation).

The relative sizes of the standardized beta coefficients let us know that, given limited resources, we will get a greater return on investment by focusing on improving the quality of neighborhoods.

Rate of Juvenile Delinquency

Quality of Parenting

Quality of theNeighborhood

Beta = .75

Beta = .32

R-square = .48

Questions?