Math 1530-017 Exam 1 With Answer Key - 2009 Page 9
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11(a) weight decreases by nearly 21 pounds for each additional inch of neck girth.
(b) weight decreases by about 246.5 pounds for each additional inch of neck girth.
(c) neck girth increases by about 20.57 inches for each additional pound of weight.
(d) neck girth is about 89% of a bear’s weight.
(e) weight increases by about 20.57 pounds for each additional inch of neck girth.
33. What is the approximate value of the correlation between neck girth and weight for this sample of
wild bears?
(a) 0.89
(b) 1.00
(c)
0.94
(d) 0.94
(e) 0.21
34. The auto insurance industry crashed some test vehicles into a cement barrier at speeds of 5 to 25
mph to investigate the amount of damage to the cars. They found a correlation of r = 0.60 between
speed (mph) and damage (in hundreds of $). How can we interpret the correlation value?
(a) 60% of the time, predicted damage ($) is equal to actual damage ($).
(b) The amount of damage seems to be positively related to the speed at which a car hits the barrier,
with higher speeds tending to correspond to larger amounts of damage ($).
(c) Predicted damage ($) changes 600 dollars for every one mph increase in speed.
(d) We would expect the damage to be equal to 60% of the mean damage.
(e) At 5 mph we would expect (0.60 × 5) × $100 = $300 damage and at 25 mph we would expect
(0.60 × 25) × $100 = $1500 damage.
35. A survey of the world’s nations in 2004 shows a strong correlation between percentage of the country
using cell phones and life expectancy in years at birth. The correlation is most likely due to:
(a) cause and effect (cell phones are good for your health).
(b) a mistake, since the correlation must be negative.
(c) “reverse” cause and effect (longer life causes more people to use cell phones).
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(d) a large r
.
(e) the effect of a lurking variable, such as general economic conditions.
36. It is difficult to determine a person’s body fat percentage accurately without immersing him or her
in water. Researchers hoping to find ways to make a good estimate immersed 20 male subjects, then
measured their waists. The correlation between the two variables is r = 0.887 and the least-squares
regression line for predicting % Body Fat from Waist (inches) is
% Body Fat =
62.6 + 2.22×Waist
The estimated % body fat for a male with a waist size of 38 inches is about
(a) 15%
(b) 25%
(c) 22%
(d) 30%
(e) 44%
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