Question

Suppose that the birth weights of infants are Normally distributed with mean 120 ounces

and a standard deviation of 18 ounces. (Note: 1 pound = 16 ounces.)

a) Find the probability that a randomly selected infant will weight less than 5 pounds.

b) What percent of babies weigh between 8 and 10 pounds at birth?

c) How much would a baby have to weigh at birth in order for him to weight in the top

10% of all infants?

d) Suppose we take a random sample of 100 babies at birth. What is the mean of their

average weight?

e) Suppose we take a random sample of 100 babies at birth. What is the standard

deviation of their average weight?

f) What is the probability that the average weight of the 100 babies (from the previous

part) will exceed 8 pounds?

g) Use Chebyshev to find an upper bound for the probability that the average weight

of 100 randomly selected babies will exceed 9.75 pounds.

Answer 1