In-Class Activity Chpt 5 | Birth Weights in America Name: a. 28 to 31 weeks 2. What percent of the babies born within each gestation period have a low birth weight (under 5.5 pounds)? X = 5.5 2 = X- U M= 3.20 0=1.02 2-z = 5.5- 3.20 = 2.25 1 .oa P(x