Transcript Decide which of the described variables likely have a

Decide which of the described variables likely
have a normal or near-normal distribution.
A. The amount of change held by a teacher at the
end of each day.
B. The amount of pocket money held by each
student at a mid-sized liberal arts college at a
given time.
C. The number of heads that show when two coins
are tossed.
a. A
b. B
c. C
d. None
Slide 5 - 1
Select the distribution that appears to be the most
normal.
a.
b.
c.
d.
Slide 5 - 2
If light bulbs have lives that are normally
distributed with a mean of 2500 hours and a
standard deviation of 500 hours, use the 68-9599.7 rule to approximate the percentage of light
bulbs having a life between 3000 hours and 3500
hours.
a. About 50%
b. About 13.5%
c. About 27%
d. About 85%
Slide 5 - 3
The lifetimes of light bulbs of a particular type are
normally distributed with a mean of 270 hours and
a standard deviation of 11 hours. What percentage
of the bulbs have lifetimes that lie within 2
standard deviations of the mean on either side?
a. 34%
b. 68%
c. 95%
d. 99.7%
Slide 5 - 4
The annual precipitation for one city is normally
distributed with a mean of 72 inches and a
standard deviation of 3.5 inches. In 95% of the
years, the precipitation in this city is between
a. 70 and 74 inches
b. 68.5 and 75.5 inches
c. 65 and 79 inches
d. 61.5 and 82.5 inches
Slide 5 - 5
At one college, GPA’s are normally distributed
with a mean of 3 and a standard deviation of 0.6.
Find the 80th percentile.
a. 3.31
b. 3.40
c. 3.51
d. 3.77
Slide 5 - 6
The volume of soda in quart soda bottles are
normally distributed with a mean of 32.3 oz and a
standard deviation of 1.2 oz. What is the
probability that the volume of soda in a randomly
selected bottle will be less than 32 oz?
a. 0.6827
b. 0.5987
c. 0.3173
d. 0.4013
Slide 5 - 7
The systolic blood pressures of the patients at a
hospital are normally distributed with a mean of
136 mm Hg and a standard deviation of 12 mm
Hg. Find the two blood pressures having these
properties: the mean is midway between them and
91.08% of all blood pressures are between them.
a. 115.6 and 156.4 mm Hg
b. 128.7 and 143.3 mm Hg
c. 125.8 and 146.2 mm Hg
d. 122.0 and 150.0 mm Hg
Slide 5 - 8
Which of the following statements concerning
areas under the standard normal curve is/are true?
a. If a z-score is negative, the area to its right is
greater than 0.5.
b. If the area to the right of a z-score is less than
0.5, the z-score is negative.
c. If a z-score is positive, the area to its left is
less than 0.5.
a. a, c
b. b, c
c. a, b
d. a
Slide 5 - 9
The mean score on the exit examination for an
urban high school is 63 with a standard deviation
of 8. What is the mean of the distribution of
sample means with a sample size of 9?
a. 60.3
b. 63
c. 65.7
d. 71
Slide 5 - 10
The weights of the fish in a certain lake are
normally distributed with a mean of 20 lb and a
standard deviation of 6. If 4 fish are randomly
selected, what is the likelihood that the mean
weight will be between 17.6 and 23.6 lb?
a. 0.3270
b. 0.4032
c. 0.6730
d. 0.0968
Slide 5 - 11
A study of the amount of time it takes a mechanic
to rebuild the transmission for a 1992 Chevrolet
Cavalier shows that the mean is 8.4 hours and the
standard deviation is 1.77 hours. Assume that a
random sample of 40 mechanics is selected and the
mean rebuild time of the sample is computed.
Assuming the mean times are normally distributed,
what percentage of sample means are greater than
9.1 hours?
a. 0.3270
b. 0.4032
c. 0.6730
d. 0.0968
Slide 5 - 12