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.
( _ , _ )

Which best describes the strength of the correlation, and what is true about the causation between the variables? it is a weak negative correlation, and it is not likely causal. it is a weak negative correlation, and it is likely causal. it is a strong negative correlation, and it is not likely causal. it is a strong negative correlation, and it is likely causal.

Write an algebraic expression to match each statement a. four less than 8 times a number b. twice the difference of a number and six c. nine from a number squared

Quick! a survey of 57 customers was taken at a bookstore regarding the types of books purchased. the survey found that 33 customers purchased mysteries, 25 purchased science fiction, 18 purchased romance novels, 12 purchased mysteries and science fiction, 9 purchased mysteries and romance novels, 6 purchased science fiction and romance novels, and 2 purchased all three types of books. a) how many of the customers surveyed purchased only mysteries? b) how many purchased mysteries and science fiction, but not romance novels? c) how many purchased mysteries or science fiction? d) how many purchased mysteries or science fiction, but not romance novels? e) how many purchased exactly two types of books?