Table 3Regression results for the outcome “confirmed malaria cases” using fixed and random effects models, with and without an instrumental variable*

Outcome variable Type of model Model 1 Confirmed malaria cases Fixed effects, no interventions Model 2 Confirmed malaria cases Fixed effects Model 3 Confirmed malaria cases Fixed effects, instrumented Model 4Confirmed malaria cases Random effects, instrumented
DDT 0.42 (11.34)† –1.589 (3.64)† –1.62 (3.58)†
Permethrin –2.108 (5.96)† –1.637 (3.10)† –1.12 (2.05)‡
Permethrin2 0.031 (2.90)‡ 0.014 (0.86) 0.004 (0.27)
Temephos –4.221 (5.11)† –0.21 (0.14) –0.124 (0.09)
Education –1.333 (4.38)† –1.785 (3.91)† –1.697 (3.67)†
Education2 0.019 (3.36)† 0.026 (3.05)‡ 0.025 (2.87)†
Proximity to water 0.142 (0.85)
Zone population 0.022 (8.95)†
Rainfall 0.054 (3.63)† 0.06 (4.28)† 0.051 (2.48)‡ 0.046 (2.15)‡
Rainfall2 –4.9 × 10−5(2.54)‡ –5.4 × 10−5(2.90)† –5.2 × 10−5(1.9) –4.5 × 10−5(1.62)
Lagged rainfall 0.019 (1.28) 0.024 (1.68) 0.018 (0.87) 0.013 (0.61)
Lagged rainfall2 –7.9 × 10−9(0) –4.5 × 10−6(0.24) –2.2 × 10−6(0.08) –7.7 × 10−6(0.27)
Seq. –0.496 (12.85)† –0.19 (4.58)† –0.729 (5.56)† –0.762 (5.60)†
Constant 40.6 (11.95)† 18.595 (4.97)† 122.323 (0) 53.191 (2.68)†
No. of observations 2,160 2,610 2,610 2,610
Permethrin χ2(P) 28.1 (P < 0.0001)§ 23.8 (P < 0.0001) 14.4 (P = 0.0007)
*

Absolute values of t-statistics are in parentheses. Seq. = sequential month number.

P< 0.01.

P< 0.05.

§

In Model 2 only joint tests are F-tests.

From: Impregnated Nets or DDT Residual Spraying? Field Effectiveness of Malaria Prevention Techniques in Solomon Islands, 1993–1999

Cover of The Intolerable Burden of Malaria II: What's New, What's Needed
The Intolerable Burden of Malaria II: What's New, What's Needed: Supplement to Volume 71(2) of the American Journal of Tropical Medicine and Hygiene.
Breman JG, Alilio MS, Mills A, editors.
Copyright © 2004, American Society of Tropical Medicine and Hygiene.

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