Assume that the length of human pregnancies from conception to birth varies according to a distribution that is approximately normal with a mean μ
=
266
μ=266 days and
σ
=
16
σ=16 days (in other words,
X
∼
N
(
266
,
16
)
X∼N(266,16). Use a calculator or Excel to find the following values.

1) What pregnancy length is less than 50% of the other pregnancy lengths?
Answer value

2) What is the 95th percentile of pregnancy lengths? Use 4 decimal places
Answer value

3) What length of pregnancy is shorter than 97.5% of all pregnancy lengths? Use 4 decimal places.
Answer value

4) Between what two numbers do the middle 70% of all pregnancy lengths fall? Use 4 decimal places.
( _ , _ )