Question

It is not surprising that babies with low birth weights are at risk for developmental difficulties, but extraoridinarily large babies also face a higher than noraml risk of medical problems. In the United States the average full term single birth baby has a weight of 3.4 kg with a standard deviation of 0.6 kg.

a) Babies below 2.5 kg in weight are considered to be high risk/low weight deliveries. Assuming birth weghts are normally distributed, what percentage of births would be in this category?

b) Babies above 4.6 in weight are considered to be high risk/high birth weight deliveries. What percentage of births would fall in this category?

c) Suppose a new study claims that only the middle 80% of the birth weights should be considered normal. What would be the new cut-off points for low and high weight risk deliveries?

****PLEASE provide steps & answers! Thanks :)

Answer 1

Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability for each Z score.

For C, use P(±.40) to find Z and insert into equation above.