<qa>  How many working class families will be selected for participation?A total of 324 working class families, representative of the primary ethnic populations in Chicago African American, Caucasian, and Mexican American, will be selected for participation. Both parents, one 4- to 6-year-old child, and one 6- to 8-year-old sibling will participate. Single parent families will also be included; the parent will be asked to nominate a second adult or an additional older sibling in place of the second parent. 