"According to the National Center for Health Statistics, in 2005 the average birthweight of a newborn baby was approximately normally distributed with a mean of 119 ounces (7 lb, 7 oz) and a standard deviation of 19 ounces." A 'low birthweight' baby is one who weighs less than 88 ounces (5 lb, 8 oz) at birth. What percentage of babies are low birthweight?
A) 5.16%
B) 44.84%
C) 55.16%
D) 94.84%

Question

"According to the National Center for Health Statistics, in 2005 the average birthweight of a newborn baby was approximately normally distributed with a mean of 119 ounces (7 lb, 7 oz) and a standard deviation of 19 ounces." A 'low birthweight' baby is one who weighs less than 88 ounces (5 lb, 8 oz) at birth. What percentage of babies are low birthweight?
A) 5.16% 
B) 44.84%
C) 55.16%
D) 94.84%

Quizplus · Accepted Answer

To find the percentage of babies that are considered low birthweight, we use the Z-score formula: Z = (X - μ) / σ, where X is the value in question (88 ounces), μ is the mean (119 ounces), and σ is the standard deviation (19 ounces). Plugging in the values gives us Z = (88 - 119) / 19 = -31 / 19 ≈ -1.63. Looking up this Z-score in a standard normal distribution table or using a calculator, we find that the percentage of babies weighing less than 88 ounces is approximately 5.16%.