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Targeted areas for police patrols have shown promising results in reducing gun violence.
- Kansas City (Sherman, Shaw, and Rogan, 1995).
- Similar projects were implemented in Indianapolis (McGarrell et al., 2001) and Pittsburgh (Cohen and Ludwig, 2003).
- Findings indicate that targeting hot spots leads to:
  - Reduction in gun-related crimes.
  - Increased seizures of illegal firearms.
Findings from Indianapolis and Pittsburgh enhance the external validity of Kansas City's results.

Concerns how well an observed relationship represents the underlying causal process.
It involves generalizing observations to real-world situations.
Example: The supervision of police officers.
- Defining "close supervision" narrowly may misrepresent broader constructs.
- Two methods of defining close supervision:
  1. Marked police presence (sergeant keeping patrol car in sight).
  2. Review of ticket production – highlights the limitations of the former definition.

Tested preventive patrol’s effectiveness via:
- Proactive beats: Twice normal patrol.
- Reactive beats: No patrol.
- Control beats: Normal patrol levels.
Results indicated no significant difference in:
- Crime rates.
- Fear of crime.
- Arrest rates.
Richard Larson (1975) identified design issues:
- Visibility of police presence not solely dependent on routine patrol.
  - Adjacent beat design enhances visibility.
  - Officers actively involved in calls increased police presence in reactive beats.

Validity threats can be categorized into:
- Bias: Systematic (alternative explanations) and nonsystematic (statistical procedures).
- Generalizability: Ensuring findings translate across varied conditions.
Four validity questions (Shadish):
1. Size and reliability of covariation between presumed cause and effect.
2. Causality of the covariation versus treatment absence.
3. Generalizability of causal relationships in varied contexts.
4. General constructs involved in observed relationships.

Investigating the potential causal relationship between drug use and crime is complex.
General Idea: Drug addiction may drive individuals to commit crimes for fulfilling their habits.

Research does not conclusively determine if drug use precedes crime or vice versa.
- Chaiken and Chaiken (1982): Found variability in timing of drug use and crime commission among inmates.
Statistical analysis:
- Drug users > 3 times more likely to engage in crime (Bennett et al., 2008).
Conclusion: Clear association exists but not necessarily direct causation due to other influencing factors.

Internal Validity: Causal statements about drug use and crime are questioned.
- Drug use and crime may be influenced by other common factors that are not directly interrelated.
Construct Validity: There is diversity in patterns of drug use and crime.
- Need to recognize varying behaviors within different populations (e.g., adolescent vs. adult behavior).

Generalizing across different types of drug usage is complex and problematic.
Uniform policies for drug reduction may not effectively impact serious crimes due to varying patterns.

Research indicates a complex relationship between drug use and crime.
Policies should recognize this complexity rather than assume a straightforward causal link.