What percent of babies born in the United States are classified as having a low birth weight (< 2,500 g)? Explain how you got your answer.

Answer:

2.5%. The z-score for 2,500 g is -2. About 95% of babies weigh between 2,500 g and 4,500 g, leaving 5% in the two tails. Since the normal distribution is symmetric, 2.5% weigh less than 2,500 g.