The birth weight of healthy, full term infants in the United States is nearly normally distributed. The mean weight is 3,500 grams, and the standard deviation is 500 grams. a. What percent of healthy newborns will weigh more than 3.250 grams? b. What weights would 95% of all healthy newborns tend to fall between? c. What is the z score for an infant who weighs 2,750 grams? apter 7