The American Academy of Pediatrics recommends a vitamin D level of at least 20 ng/ml for infants. The article "Vitamin D and Parathormone Levels of Late-Preterm Formula Fed Infants During the First Year of Life" (European J. of Clinical Nutr., 2012: 224-230) reported that for a sample of 102 preterm infants judged to be of appropriate weight for their gestational age, the sample mean vitamin D level at 2 weeks was 21 with a sample standard deviation of 11. Does this provide convincing evidence that the population mean vitamin D level for such infants exceeds 20? Test the relevant hypotheses using a significance level of .10.