Statistical analysis

The SPSS statistical software program version 21.0 (IBM Inc, Chicago, IL) was used for the statistical analysis. Values were assessed for normality by checking for skewness. Results were expressed as mean ± SD. Independent sample t-test was used to determine differences between children with EBLL and control. Pearson’s product moment correlation analysis was used to evaluate the relationship among BLL, erythrocyte AChE activity and IQ. Step-wise Multiple Regression Analysis was used to model cause-effect relationship between BLL (independent variable) and the erythrocyte AChE activity and IQ (dependent variables). All tests were 2-tailed and p-value <0.05 was considered as statistically significant.