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.

• Between what two weights do the middle 68% of newborns in the US weigh according to the 68-95-99.7 rule?

3250 – 550 = 2700 g

and 3250 + 550 = 3800g.