statistics
posted by ryee .
the birth of healthy, full term infants in the United States is nearly normally distributed. The mean weight is 3,500 grams, and the standard deeviation is 500 grams.
(a) what percentage of the healthy newborns will weigh more than 3,250 grams?
(b) what weightswould 95% of all healthy newborns tend to fall between?
(c)what is the z score for an infant who weighs 2,750 grams?

(c) Z = 750/500 = 1.25
For the others, you need a normal distribution probability calculator or table.
There are many online. There is a good one at
http://www.stat.tamu.edu/~west/applets/normaldemo.html
It says that the answer to (a) is 69.15%