1. Economics 172 Issues in African Economic Development
Lecture 6
February 2, 2006

2. Miguel and Kremer (2004) – worms and education
Outline:
Methodological issues: Omitted variable bias and randomized experiments
Miguel and Kremer (2004) – worms and education
Economics 172

3. Omitted variable bias in OLS
(1) Yi = a + bTi + cXi + ei
Economics 172

4. Omitted variable bias in OLS
(1) Yi = a + bTi + cXi + ei
Economics 172

5. Omitted variable bias in OLS
(1) Yi = a + bTi + cXi + ei
Economics 172

6. Omitted variable bias in OLS
Economics 172

7. Omitted variable bias in OLS
(1) Yi = a + bTi + cXi + ei
(2) E(Yi | T=1) – E(Yi | T=0)
= [a + b + E(Xi | Ti=1) + E(ei | Ti=1)]
– [a E(Xi | Ti=0) + E(ei | Ti=0)]
= b + c [E(Xi | Ti=1) – E(Xi | Ti=0)]
Economics 172

8. Economics 172

9. Miguel and Kremer (2004)
Primary School Deworming Project (PSDP) in Kenya
Economics 172

10. Economics 172

11. Miguel and Kremer (2004)
Primary School Deworming Project (PSDP) in Kenya
Randomized design:
Group 1 (25 schools) Treatment Treatment
Group 2 (25 schools) Comparison Treatment
Group 3 (25 schools) Comparison Comparison
Economics 172

12. Economics 172

13. PSDP Baseline differences (1998)
Group 1 Group 2 Group 3
Latrine at home
Livestock at home
Child sick often
(self-reported)
1996 exam score
(normalized mean 0, s.d. 1)
Economics 172

14. Health, nutrition impacts (1999)
Group 1 Group 2 G1–G2
Rate of moderate-heavy infection *
Sick in past week *
Height for age *
(Z-score)
Hemoglobin (Hb)
Economics 172

15. Within-school infection externalities (1999)
Group 1 Group 1 Group 2
(Treated) (Untreated)
Rate of moderate-heavy Infection, 1999
Economics 172

16. Within-school infection externalities (1999)
Group 1 Group 1 Group 2
(Treated) (Untreated)
Rate of moderate-heavy Infection, 1999
Rate of moderate-heavy Infection, 1998
Economics 172

17. Economics 172

18. Whiteboard #1
Economics 172

19. Whiteboard #2
Economics 172

20. Whiteboard #3
Economics 172

21. Whiteboard #4
Economics 172

22. Whiteboard #5
Economics 172

23. Map of Africa
Economics 172