Table 3.
Interaction effects of allocation to trial interventions (information, subsidies, and incentives for reducing anaemia) with pre-existing incentives for school principals to achieve good academic performance among students on haemoglobin (Hb) concentration and anaemia prevalence
| Trial arms compared* | Without incentive for good academic results (n=2871 students, 58 schools)† | With incentive for good academic results (n=682 students, 14 schools)‡ | Interaction effect§ | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Change in Hb concentration (g/L)¶ | Anaemic at follow-up (Hb <115 g/L)** | Change in Hb concentration (g/L) | Anaemic at follow-up (Hb <115 g/L) | Change in Hb concentration (g/L) | Anaemic at follow-up (Hb <115 g/L) | ||||||||||||
| Marginal effect (95% CI) | P value | Marginal effect (95% CI) | P value | Marginal effect (95% CI) | P value | Marginal effect (95% CI) | P value | Difference (95% CI) | P value | Difference (95% CI) | P value | ||||||
| Information v control | –0.6 (–3.2 to 2.0) | 0.66 | 0.02 (–0.03 to 0.07) | 0.46 | 9.2 (4.0 to 14.4) | <0.01 | –0.09 (–0.14 to –0.03) | <0.01 | 9.8 (4.1 to 15.5) | <0.01 | –0.11 (–0.19 to –0.03) | 0.01 | |||||
| Subsidy v control | –0.2 (–2.8 to 2.5) | 0.91 | –0.01 (–0.06 to 0.04) | 0.65 | 2.6 (–2.5 to 7.7) | 0.32 | –0.04 (–0.10 to 0.02) | 0.24 | 2.7 (–3.1 to 8.6) | 0.35 | –0.03 (–0.10 to 0.05) | 0.51 | |||||
| Incentive v control | 1.1 (–1.4 to 3.6) | 0.38 | –0.03 (–0.07 to 0.01) | 0.12 | 9.7 (3.7 to 15.6) | <0.01 | –0.09 (–0.15 to –0.03) | <0.01 | 8.6 (2.1 to 15.1) | 0.01 | –0.06 (–0.12 to 0.01) | 0.07 | |||||
| Subsidy v information | 0.4 (–2.6 to 3.4) | 0.78 | –0.03 (–0.09 to 0.03) | 0.30 | –6.6 (–12.6 to –0.6) | 0.03 | 0.05 (–0.01 to 0.11) | 0.09 | –7.0 (–13.7 to –0.4) | 0.04 | 0.08 (–0.00 to 0.17) | 0.06 | |||||
| Incentive v information | 1.7 (–1.2 to 4.5) | 0.25 | –0.05 (–0.11 to 0.00) | 0.07 | 0.5 (–6.3 to 7.3) | 0.89 | –0.00 (–0.03 to 0.03) | 0.94 | –1.2 (–8.6 to 6.1) | 0.75 | 0.05 (–0.01 to 0.11) | 0.11 | |||||
| Incentive v subsidy | 1.3 (–1.6 to 4.1) | 0.39 | –0.02 (–0.07 to 0.03) | 0.42 | 7.1 (0.3 to 13.9) | 0.04 | –0.05 (–0.12 to 0.01) | 0.09 | 5.8 (–1.5 to 13.2) | 0.12 | –0.03 (0.04 to 0.04) | 0.40 | |||||
*Control arm (no intervention); information arm (school principals received information about anaemia); subsidy arm (principals received information and unconditional subsidies for reducing anaemia); incentive arm (principals received information, subsidies, and financial incentives for reducing anaemia).
†Marginal treatment effects evaluated for schools where principal did not have bonus incentives based on student academic performance.
‡Marginal treatment effects evaluated for schools where principal had bonus incentives based on student academic performance.
§Interaction effect is the difference in marginal treatments effects between schools in which principals had bonus incentives for academic performance and those in which they did not.
¶Results for change in Hb concentration between baseline and follow-up are estimated with multilevel mixed effect linear regression adjusting for baseline Hb status, whether the principal is eligible for a bonus based on academic performance, student sex, student age, whether the student boards at school, mother’s migration status, and mother’s education level and clustering at the school and county level.
**Results for anaemia status at follow-up are estimated with multilevel mixed effect logistic regression adjusting for baseline Hb status, whether the principal is eligible for a bonus based on academic performance, student sex, student age, whether the student boards at school, mother’s migration status, and mother’s education level and clustering at the school and county level.