Question

3.The lengths of pregnancies are normally distributed with a mean of 267 days and a standard deviation of 15 days. a. Find the probability of a pregnancy lasting 309 days or longer. b. If the length of pregnancy is in the lowest 3​%, then the baby is premature. Find the length that separates premature babies from those who are not premature.
a. The probability that a pregnancy will last 309 days or longer is
b. Babies who are born on or before how many days are considered premature.

Answer 1

µ = 267

sd = 15

a)

                               

                                = P(Z > 2.8)

                                = 1 - P(Z < 2.8)

                                = 1 - 0.9974

                                = 0.0026

b)

or, x = 267 - 0.52 * 15

or, x = 259.2 or 259 (ans)