A study on the effect of maternal vitamin D supplementation on neonatal serum calcium was conducted.164 breast feeding mums took part and 82 were randomly allocated to the supplement group and the remaining 82 were allocated to a placebo.164 bottle feeding mums took part and 82 were randomly allocated to the supplement group and the remaining 82 were allocated to a placebo.Serum calcium concentrations (mmol/l) in one-week babies was recorded.Describe the structure of the study (independent variables, dependent variable) and detail why the researchers would have used random allocation.