Download 1 A certain brand of flood lamps has a lifetime that is normally

Name: __________________
1
Class:
Date: _____________
A certain brand of flood lamps has a lifetime that is normally distributed with a mean of 3,750 hours and a standard deviation of
300 hours. What proportion of these lamps will last for more than 4,000 hours?
Enter your answer to four decimal places.
_________
2
A certain brand of flood lamps has a lifetime that is normally distributed with a mean of 3,750 hours and a standard deviation of
300 hours. What proportion of these lamps will last less than 3,600 hours?
Enter your answer to four decimal places.
_________
3
A certain brand of flood lamps has a lifetime that is normally distributed with a mean of 3,750 hours and a standard deviation of
300 hours. What proportion of these lamps will last between 3,800 and 4,100 hours?
Enter your answer to four decimal places.
_________
4
A certain brand of flood lamps has a lifetime that is normally distributed with a mean of 3,750 hours and a standard deviation of
300 hours. What lifetime should the manufacturer advertise for these lamps in order that only 2% of the lamps will burn out before
the advertised lifetime?
_________
5
hours
The standard error of the mean:
a. is never larger than the
standard deviation of the
population.
6
b. decreases as the
sample size
increases.
c. measures the variability
of the mean from sample
to sample.
d. All of these
choices.
True-False.
The central limit theorem is basic to the concept of statistical inference, because it permits us to draw conclusions about the
population based strictly on sample data, and without having any knowledge about the distribution of the underlying population.
7
In a given year, the average annual salary of a NFL football player was $205,000 with a standard deviation of $24,500. If a simple
random sample of 50 players was taken, what is the probability that the sample mean will exceed $210,000?
Enter your answer to four decimal places.
_________
PAGE 1
Name: __________________
8
Class:
Date: _____________
The heights of men in the USA are normally distributed with a mean of 68 inches and a standard deviation of 4 inches. What is
the probability that a randomly selected man is taller than 70 inches.
Enter your answer to four decimal places.
_________
9
The heights of men in the USA are normally distributed with a mean of 68 inches and a standard deviation of 4 inches. A random
sample of five men is selected. What is the probability that the sample mean is greater than 70 inches?
Enter your answer to four decimal places.
_________
10 The heights of men in the USA are normally distributed with a mean of 68 inches and a standard deviation of 4 inches. What is
the probability that the mean height of a random sample of 36 men is greater than 70 inches?
Enter your answer to four decimal places.
_________
PAGE 2
ANSWER KEY
Lueker Summer2008 HW5
1. 0.2033
2. 0.3085
3. 0.3115
6. True
7. 0.0749
8. 0.3085
ANSWER KEY - Page 1
4. 3132
9. 0.1314
5. d
10. 0.0013