"twins" <-
structure(list(Foster = c(82, 80, 88, 108, 116, 117, 132, 71, 
75, 93, 95, 88, 111, 63, 77, 86, 83, 93, 97, 87, 94, 96, 112, 
113, 106, 107, 98), Biological = c(82, 90, 91, 115, 115, 129, 
131, 78, 79, 82, 97, 100, 107, 68, 73, 81, 85, 87, 87, 93, 94, 
95, 97, 97, 103, 106, 111), Social = structure(c(1, 1, 1, 1, 
1, 1, 1, 3, 3, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 
2, 2), .Label = c("high", "low", "middle"), class = "factor")), .Names = c("Foster", 
"Biological", "Social"), class = "data.frame", row.names = c("1", 
"2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", 
"14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", 
"25", "26", "27"))