7.3 Evaluation of effectiveness: Measurement data of indexes(Growth rate of height, weight and head circumference at 4,8,12 week, defication frequency) should be analyzed by normality test firstly. If data conforms to normal distribution, the comparation between formula milk group (commercially available formula subgroup and Friso formula subgroup) and breast milk group should be analysed by One-Way ANOVA method. LSD method is used for multiple comparisons. If data does not conform to normal distribution, then Wilcoxon Rank-Sum test is used. A level of significance is α=0.05 (two-tailed). Frequency data of indexes ( incidence of constipation at 4,8,12 week, eyes secretion) is recorded as cases or percentage. If theoretical frequency <5 or total observed frequency <30, Fisher's exact probability method is used; otherwise Chi-square test is used. A level of significance is α=0.05 (two-tailed).