Parenting, Custody and Realistic Risk Assessment

Which is more risky for a nine-year old: letting the child wait alone at a bus stop for ten minutes, in mid-day, or letting the same child ride a bicycle for a half hour near his house? How about letting the same child visit a friend who has a swimming pool? A friend whose parent owns firearms and keeps them in the house? (See Dubner and Levitt's Freakonomics for that dyad.) Which are most parents likely to think are acceptable and appropriate? Which are judges likely to think demonstrate responsible or irresponsible parenting?

Should parents or judges make these calls based on their "gut sense" or "intuition", or should real EVIDENCE be required before the court injects itself into this sort of decision?