Introduction to the Practice of Statistics 9th edition by David S. Moore Test bank
E)The area under a density curve above any range of values is the proportion of all observations that fall in that range.
186.The following curve is to be a density curve for the variable x.
What must be the value of the point on the vertical axis labeled H for this to be a proper density function?
A)1.60
B)1.00
C)0.80
D)1.25
E)0.625
187.Which one of the following statements about the mean and the median of a density curve is FALSE?
A)The median is the point on the axis that divides the area under the density curve in two equal halves.
B)The median and the mean have the same value if the density curve is symmetric.
C)The mean is the “balance point” of the density curve.
D)The median of a skewed density curve is pulled away from the mean in the direction of the long tail.
E)For a symmetric density curve, both the mean and the median are at the center of the curve.
188.For the density curve displayed below, what is the mean?
A)0.25
B)0.50
C)0.71
D)0.75
189.Determine whether each of the following statements regarding a Normal density curve is true or false.
A) It is symmetric.
B) It has a peak centered above its mean.
C) The quartiles lie 1 standard deviation below and above the mean.
D) The spread of the curve is proportional to the standard deviation.
190.Many residents of suburban neighborhoods own more than one car but consider one of their cars to be the main family vehicle. The age of these family vehicles can be modeled by a Normal distribution with a mean of 2 years and a standard deviation of 6 months. What percentage of family vehicles is between 1 and 3 years old?
A)This cannot be determined based on the information given.
B)68%
C)95%
D)99.7%
191.Many residents of suburban neighborhoods own more than one car but consider one of their cars to be the main family vehicle. The age of these family vehicles can be modeled by a Normal distribution with a mean of 2 years and a standard deviation of 6 months. What is the standardized value for a family vehicle that is 3 years and 3 months old?
A)0.22
B)2.5
C)2.6
D)2.92
192.Items produced by a manufacturing process are supposed to weigh 90 grams. However, there is variability in the items produced, and they do not all weigh exactly 90 grams. The distribution of weights can be approximated by a Normal distribution with a mean of 90 grams and a standard deviation of 1 gram. What percentage of the items will either weigh less than 87 grams or more than 93 grams?
A)6%
B)94%
C)99.7%
D)0.3%
193.The time to complete an exam is approximately Normal with a mean of 70 minutes and a standard deviation of 10 minutes. Using the 68-95-99.7 rule, what percentage of students will complete the exam in under an hour?
A)68%
B)32%
C)16%
D)5%
194.Using the standard Normal distribution tables, what is the area under the standard Normal curve corresponding to Z < 1.1?
A)0.1357
B)0.2704
C)0.8413
D)0.8643
195.Using the standard Normal distribution tables, what is the area under the standard Normal curve corresponding to Z > –1.22?
A)0.1151
B)0.1112
C)0.8849
D)0.8888
196.Using the standard Normal distribution tables, what is the area under the standard Normal curve corresponding to –0.5 < Z < 1.2?
A)0.3085
B)0.8849
C)0.5764
D)0.2815
197.The variable Z has a standard Normal distribution. Find the value z such that 85% of the observations fall below z.
A)z = –1.04
B)z = 0.80
C)z = 0.85
D)z = 1.04
198.The variable Z has a standard Normal distribution. Find the value z such that the event Z > z has proportion of 0.08.
A)z = –1.41
B)z = 0.53
C)z = 0.82
D)z = 1.41
199.The temperature at any random location in a kiln used for manufacturing bricks is Normally distributed with a mean of 1000°F and a standard deviation of 50°F. If bricks are fired at a temperature above 1125°F, they will crack and must be discarded. If the bricks are placed randomly throughout the kiln, what is the percentage of bricks that crack during the firing process?