=+1 for those who participated in Head Start and 0 for children in the control group. The data are shown in Table 3. These are data from 303 children from an early Head Start evaluation, 148 who attended Head Start in the summer and 155 who did not. To understand why the example is so controversial, note the correlation between Head Start and the two cognitive outcomes: both are negative (–.10, –.09), suggesting that Head Start may have negative effects on Ability! The model is one of several possible models designed to determine what the outcomes of Head Start are after taking the family’s background characteristics into account. The correlations and SDs are also included in the Excel file “head start.xls.” All continuous variables are standardized.