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

Suppose birth weights of human babies are normally distributed
with a mean of 120 ounces and a stdev of 16 ounces (1lb = 16
ounces).
1. What is the probability that a baby is at least 9 lbs 11
ounces? 2. What is the probability that a baby weighs less than 10
lbs (160 ounces)? 3. What weight is the 90th percentile?

4. Suppose the birth weights of babies in the USA are normally
distributed, with mean 7.47 lb and standard deviation 1.21 lb. a.
Find the probability that a randomly chosen baby weighed between
6.4 and 8.1 pounds. (Show work.) b. Suppose a hospital wants to try
a new intervention for the smallest 4% of babies (those with the
lowest birth weights). What birth weight in pounds is the largest
that would qualify for this group? (Show your work.)

The birth weight of newborn babies is normally distributed with
a mean of 7.5 lbs and a standard deviation of 1.2 lbs.
a. Find the probability that a randomly selected newborn baby
weighs between 5.9 and 8.1 pounds. Round your answer to 4 decimal
places.
b. How much would a newborn baby have to weigh to be in the top
6% for birth weight? Round your answer to 1 decimal place.

It is known that the birth weight of newborn babies in
the U.S. has a mean of 7.1 pounds with a standard deviation of 1.5
pounds. Suppose we randomly sample 36 birth certificates from the
State Health Department, and record the birth weights of these
babies.
The sampling distribution of the average birth weights
of random samples of 36 babies has a mean equal to ______ pounds
and a standard deviation of ______ pounds.
What is the probability the...

It is known that the birth weight of newborn babies in the U.S.
has a mean of 7.1 pounds with a standard deviation of 1.5 pounds.
Suppose we randomly sample 36 birth certificates from the State
Health Department, and record the birth weights of these
babies.
The sampling distribution of the average birth weights of
random samples of 36 babies has a mean equal to ______
pounds and a standard deviation of ______ pounds.
What is the probability the average...

Suppose the weights of Farmer Carl's potatoes are normally
distributed with a mean of 8.1 ounces and a standard deviation of
1.2 ounces.
(a) If 5 potatoes are randomly selected, find the probability
that the mean weight is less than 9.8 ounces.
Round your answer to 4 decimal places.
(b) If 8 potatoes are randomly selected, find the probability that
the mean weight is more than 9.4 ounces.
Round your answer to 4 decimal places.

Suppose the weights of Farmer Carl's potatoes are normally
distributed with a mean of 7.9 ounces and a standard deviation of
1.3 ounces.
(a) If 4 potatoes are randomly selected, find the probability
that the mean weight is less than 9.3 ounces.
Round your answer to 4 decimal places.
(b) If 7 potatoes are randomly selected, find the probability
that the mean weight is more than 8.5 ounces.
Round your answer to 4 decimal places.

Suppose the weights of Farmer Carl's potatoes are normally
distributed with a mean of 7.8 ounces and a standard deviation of
1.2 ounces.
(a) If 5 potatoes are randomly selected, find the probability
that the mean weight is less than 8.9 ounces.
Round your answer to 4 decimal places.
(b) If 7 potatoes are randomly selected, find the probability that
the mean weight is more than 9.2 ounces.
Round your answer to 4 decimal places.

Birth weights in the United States have a distribution that is
approximately normal with a mean of 3396 g and a standard deviation
of 576 g. Apply Table A-2 or statistics technology you can use to
answer the following questions:
(a) One definition of a premature baby is the the birth weight
is below 2500 g. If a baby is randomly selected, find the
probability of a birth weight below 2500 g.
(b) Another definition of a premature baby is...

Birth weights in the United States have a distribution that is
approximately normal with a mean of 3396 g and a standard deviation
of 576 g. Apply Table A-2 or statistics technology you can use to
answer the following questions:
(a) One definition of a premature baby is the the birth weight
is below 2500 g. If a baby is randomly selected, find the
probability of a birth weight below 2500 g.
(b) Another definition of a premature baby is...

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