Question

a. The number of hours of sleep per night that adults in the United States is normally distributed with a mean of 6.8 hours and a standard deviation of 1.4 hours. If the recommended amount of sleep is 7 hours, what proportion of US adults are getting less than that amount of sleep? Round to the nearest ten-thousandth.

b. The number of hours of sleep per night that adults in the United States is normally distributed with a mean of 6.8 hours and a standard deviation of 1.4 hours. Out of 100 US adults, how many would you expect to get between 8 and 9 hours of sleep? Round to the nearest whole number. We would expect ___ adults to get between 8 and 9 hours of sleep.

c.The number of hours of sleep per night that adults in the United States is normally distributed with a mean of 6.8 hours and a standard deviation of 1.4 hours. What number of hours of sleep is at the 30th percentile? Round to the nearest ten-thousandth (4 decimal places).___ hours is at the 30th percentile.

d. The number of hours of sleep per night that adults in the United States is normally distributed with a mean of 6.8 hours and a standard deviation of 1.4 hours. Would it be considered unusual for a person to get at least 9 hours of sleep? Why or why not?

It ["would not", "would"] be unusual since the probability is ["greater than", "less than", "equal to"] 0.05.

e. The number of hours of sleep per night that adults in the
United States is normally distributed with a mean of 6.8 hours and
a standard deviation of 1.4 hours. A simple random sample of 100
people is selected. What is the probability that the *mean of
the sample* is greater than 7 hours? Round to the nearest
ten-thousandth

Answer #1

The
number of hours adults sleep per night is normally distributed with
a mean it 5.5 hours. Assume that the standard deviation is
unknown.
If
75% of adults sleep more than 5.1 hours per night, what is the
variance?

The number of hours adults sleep per night is normally
distributed with a mean of 6.7 hours. Assume that the standard
deviation is unknown. If 75% of adults sleep more than 6.2 hours
per night, what is the variance?

A researcher wants to determine how many hours of sleep adults
get per night. She asks a random sample of 32 adults how many hours
of sleep they get per night. The mean of their answers is 7.1
hours, and the standard deviation is 1.5 hours. Make a 95%
confidence interval for the mean number of hours of sleep per night
for adults. Round the end points of the confidence interval to 2
decimal points.

The number of sleep hours for adults is normally distributed
with mean 7 hours and standard deviation 1.7 hours. What
is the probability that the mean sleep hours of a random sample of
25 adults is less than 6 hours?

The results of a national survey showed that on average, adults
sleep 7.2 hours per night. Suppose that the standard deviation is
1.4 hours and that the number of hours of sleep follows a
bell-shaped distribution. If needed, round your answers to two
decimal digits. If your answer is negative use “minus sign”.
(a)
Use the empirical rule to calculate the percentage of individuals
who sleep between 4.4 and 10 hours per day.
Enter your answer as a percentage.
%...

Suppose college students average 7.3 hours of sleep per night
with a standard deviation of 45 minutes, and suppose that this is
normally-distributed.
What is the probability that a randomly-selected college student
sleeps for more than 8.1 hours?
Probability =
What is the 60th percentile for college-student sleep times?
Round your answer to four decimal places.
60th percentile = hours

Based on a random sample of 1120 adults, the mean amount of
sleep per night is 8.91 hours. Assuming the population standard
deviation for amount of sleep per night is 3.2 hours, construct
and interpret a 95% confidence interval for the mean amount of
sleep per night.
A 95% confidence interval is (___,___)

The results of a national survey showed that on average, adults
sleep 7.1 hours per night. Suppose that the standard deviation is
1.5 hours and that the number of hours of sleep follows a
bell-shaped distribution. If needed, round your answers to two
decimal digits. If your answer is negative use “minus sign”.
(a)
Use the empirical rule to calculate the percentage of
individuals who sleep between 4.1 and 10.1 hours per day.
Enter your answer as a percentage.
%...

The results of a national survey showed that on average, adults
sleep 6.9 hours per night. Suppose that the standard deviation is
1.1 hours and that the number of hours of sleep follows a
bell-shaped distribution. If needed, round your answers to two
decimal digits. If your answer is negative use “minus sign”.
(a)
Use the empirical rule to calculate the percentage of
individuals who sleep between 4.7 and 9.1 hours per day.
Enter your answer as a percentage.
%...

The results of a national survey showed that on average, adults
sleep 7.4 hours per night. Suppose that the standard deviation is
1.1 hours and that the number of hours of sleep follows a
bell-shaped distribution. If needed, round your answers to two
decimal digits. If your answer is negative use “minus sign”.
(a) Use the empirical rule to calculate the percentage of
individuals who sleep between 5.2 and 9.6 hours per day. Enter your
answer as a percentage. %...

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