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. Author manuscript; available in PMC: 2011 Jul 1.
Published in final edited form as: Soc Sci Med. 2010 Mar 17;71(2):324–334. doi: 10.1016/j.socscimed.2010.02.027

Table 5.

Fixed-effects (within child) estimates of the cognitive PCA score.

Dependant variable is cognitive function PCA score
Fixed-effects models (within child)
Variables (1) (2) (3) (4) (5)
Asymptomatic Malaria and Malaria Parasitaemia
  Asymptomatic Malaria (active follow-up) −0.186***
(0.056)
  Lagged Asymptomatic Malaria (active follow-up) −0.109**
(0.051)
  Monthly Geom Mean P. falciparum Parasitaemia (/1000) . −0.032***
(0.010)
  Lagged Monthly Geom Mean P. falciparum Parasitaemia (/1000) . −0.019**
(0.009)
  P. falciparum Parasitaemia thresholds (active follow-up)
     500 . . −0.277***
(0.063)
     Lagged 500 . . −0.202***
(0.055)
     1000 . . . −0.341***
(0.076)
     Lagged 1000 . . . −0.251***
(0.062)
     1200 . . . . −0.354***
(0.077)
     Lagged 1200 . . . . −0.259***
(0.065)
Clinical Malaria control Dummies
  Clinical Malaria (between two active follow-
  ups or during active follow-up)		 −0.535***
(0.070)		 −0.542***
(0.070)		 −0.524***
(0.070)		 −0.519***
(0.069)		 −0.515***
(0.069)
  Lagged Clinical Malaria (between two
  active follow-ups or during active follow-		 −0.230***
(0.058)		 −0.205***
(0.061)		 −0.224***
(0.058)		 −0.212***
(0.058)		 −0.213***
(0.058)
Chronic Malaria and Malaria anemia control Variables
  Splenomegaly −0.301***
(0.116)		 −0.250**
(0.119)		 −0.235**
(0.114)		 −0.239**
(0.113)		 −0.234**
(0.113)
  Lagged Splenomegaly −0.221**
(0.103)		 −0.173*
(0.104)		 −0.201**
(0.102)		 −0.193*
(0.102)		 −0.196*
(0.102)
  Malarial anemia
     Mild −0.136
(0.091)		 −0.199**
(0.089)		 −0.170*
(0.087)		 −0.165*
(0.089)		 −0.175**
(0.088)
     Moderate 0.479***
(0.173)		 0.497***
(0.167)		 0.675***
(0.157)		 0.591***
(0.160)		 0.583***
(0.161)
  Lagged Malarial anemia
     Mild −0.142*
(0.076)		 −0.183**
(0.072)		 −0.140*
(0.073)		 −0.137*
(0.073)		 −0.144**
(0.073)
     Moderate −0.313*
(0.188)		 −0.318*
(0.180)		 −0.253
(0.180)		 −0.236
(0.180)		 −0.231
(0.180)
Health control
  Haemoglobin concentration −0.024
(0.024)		 −0.028
(0.024)		 −0.027
(0.024)		 −0.027 (0.024) −0.030
(0.024)
Intercept 0.784***
(0.300)		 0.750**
(0.298)		 0.780***
(0.296)		 0.757***
(0.293)		 0.793***
(0.295)
Number of observations 1567 1567 1567 1567 1567
Number of Children 227 227 227 227 227
R squared 0.104 0.103 0.116 0.118 0.119
Breush Pagan F-test 15.34*** 15.28*** 15.69*** 15.69*** 15.63***
Hausman specification test 170.56*** 257.35*** 259.85*** 306.52*** 312.10***

Notes. - Huber White standard errors are reported in parenthesis. Results are not changed when standard errors are clustered at the household level (not presented here). Reference category for Malarial anemia is no malarial anemia. Breush Pagan Lagrangian multiplier test for the presence of individual specific effects. The Hausman specification test compares the fixed versus random effects under the null hypothesis that the individual effects are uncorrelated with the other regressors in the model (Hausman, 1978). If correlated (H0 is rejected), a random effect model produces biased estimators, violating one of the Gauss-Markov assumptions; So a fixed effect model is preferred.

***

denotes statistical significance at t he 1% level.

**

denotes statistical significance at the 5% level.

*

denotes statistical significance at the 10% level.