Chi-square tests revealed no significant differences in terms of ethnicity (χ2 =4.974, p = .083, free or reduced lunch status (χ2=2.126, p = .163), and design status (χ2 =1.145, p = .766) between the 545 who provided both phenotypic and genetic data and those who did not. T-tests revealed no differences between these groups in terms of age at entrance to first grade. However, those included in this study were more likely to be female compared to those not included in this study (χ2= 7.473, p = .007).
