Data analyses. For statistical analysis, the software package SPSS for Windows
(version 12.0.1; SPSS, Inc., Chicago, Ill.) was used. All values were checked for
normality by visual inspection of the normal probability plots. Differences were
tested with paired sample t tests, and if P was 0.05 the difference was considered
statistically significant. Although the breast-fed group is compared to the
formula groups, it has to be kept in mind that no complete randomization was
obtained because it is not possible to double blindly assign infants to a breast-fed
group.