In a study of mother–infant interaction, mothers are rated by trained observers on the quality of their interactions with their infants. Mothers are classified on the basis of whether or not this was their first child (primiparous versus multiparous) and on the basis of whether this was a low-birthweight (LBW) infant or normal-birthweight (NBW) infant. Mothers of LBW infants were further classified on the basis of whether or not they were under 18 years old. The data represent a score on a 12-point scale; a higher score represents better mother–

infant interaction. Run and interpret the appropriate analysis of variance.