1. 1 Introduction to Research Methods How we come to know about crime

2. 2 Why Study Crime? To learn about the causes of crime Make predictions about criminal behavior Provide information to policy makers

3. 3 The Desire to Generalize Goal: External Validity –We seek knowledge that is generalizable to some larger group Method: Random sampling –Yields a representative set of observations –Each member of the population has an equal chance of being measured

4. 4 Statistical Significance A result is statistically significant if the probability that it is due to chance is less than 5% (α =.05), p <.05

5. 5 What Is a Variable? VariableAttributes/Values young, middle-aged, old male, female plumber, lawyer, professor Race Social Class

6. 6 Describing Variables Measures of Central tendency AgeNumber 13X X XX X XX 14X XX 15X XX 16X X X X 17X X 18X Mode = 16 Median = 15.5 Arithmetic Mean (Average) = (ΣY i )/N = 392/26 = 15.07 13

7. 7 Two Kinds of Variables Dependent variable: what we wish to explain or understand (crime, violence) Independent variable: what we think explains the dependent variable (poverty, age, associating with other criminals) Independent variable Dependent Variable

8. 8 Temporal Order Research Designs Cross-Sectional: Gather data all at once Longitudinal: Gather data over time to ensure proper causal ordering UnemploymentProperty Crime Unemployment

9. 9 Measures of Association: Correlation Do values on one variable correspond to values on another variable? If no, correlation = 0 If yes –Correlation = +1.0 –Correlation = -1.0

10. 10 Positive Correlation: Poverty and Homicide in Chicago Poverty Homicide Rate r =.51

11. 11 Negative Correlation: Neighborhood Satisfaction and Poverty Poverty Neighborhood Satisfaction r = -.66

12. 12 No Correlation: Social Ties and Poverty in Chicago Poverty Social Ties r =.02

13. 13 Crosstabulation: Homicide by Poverty in Chicago Low Poverty High Poverty Total Low Homicide 109 56.8% 19 12.7% 128 37.4% High Homicide 83 43.2% 131 87.3% 214 62.6% Total192150342 Positive Relationship

14. 14 Neighborhood Satisfaction by Poverty in Chicago Low Poverty High Poverty Total Low Satisfaction 55 28.6% 123 82.0% 178 52.0% High Satisfaction 137 71.4% 27 18.0% 164 48.0% Total192150342 Negative Relationship

15. 15 Social Ties by Poverty in Chicago Low Poverty High Poverty Total Low Homicide 101 52.6% 75 50.0% 176 51.5% High Homicide 91 47.4% 75 50.0% 166 48.5% Total192150342 No Relationship

16. 16 WARNING: Correlation = Causation Ice CreamMurder Season Ice CreamMurder “Spuriousness”

17. 17 Criteria of Causality Temporal order Covariation No plausible alternative explanation –Association between two variables is not the result of some other variable causing them both –The relationship between the independent and dependent is not spurious

18. 18 Drawing Causal Diagrams

19. 19 Data Gathering Methods Survey Methods Field Observation (ethnography) Unobtrusive Measurement

20. 20 Gender Discrimination at XYZ University? MalesFemalesTotal Accepted82 75% 28 25% 110 50% Denied28 25% 82 75% 110 50% Total110 220 XYZ University has 2 colleges: Liberal Arts and Engineering

21. 21 College of Liberal Arts MalesFemalesTotal Accepted2 20% 20 20% 22 20% Denied8 80% 80 80% 88 80% Total10100110

22. 22 College of Engineering MalesFemalesTotal Accepted80 80% 8 80% 88 80% Denied20 20% 2 20% 22 20% Total10010110

23. 23 Conclusion There is no gender discrimination at XYZ! Women tend to apply to departments that have higher rejection rates Moral of story: control variables Simpson’s paradox

24. 24 Experimental Research Design Experimental Group Control Group Measure DV RANDOM ASSIGNMENT Test Remeasure DV Compare

25. The Scientific Study of Crime Theory Written explanation of why things happen Observation Scientific methods for observing what happens EmpiricalHypotheses Generalizations