Example: Birth weights of babies in the US have a normal distribution with a mean of 3250 grams and a standard deviation of 550 grams.
3250 – 550 = 2700 g
and 3250 + 550 = 3800g.
3250 – 2(550) = 2150 g
and 3250 + 2(550) = 4350g.
c. What proportion of newborn in the US weigh more than 4350g?
P(weights > 4350) = 0.025.