Weights of newborn babies in the United States are normally distributed with a mean of 3420 grams and a standard deviation of 495 grams.
a) A newborn weighing less than 2200 grams is considered to be at risk. What fraction of newborn babies are in the “at risk” category?
b) What middle interval of weights includes 0.90 fraction of newborn babies?
c) What fraction of newborn babies' weights is within ±2 standard deviations from the population mean weight?
d) In Norway the fraction of newborn babies who weight less than 2200 grams is 0.0031. The standard deviation of weights is 500 grams. What is the mean weight of newborn babies?