Chapter 2 Practice Quiz

Many professional schools require applicants to take a standardized test. Suppose that 1000 students take such a test. Several weeks after the test, Pete receives his score report: he got a 63, which placed him at the 73rd percentile. This means that:

• Pete did worse than about 63% of the test takers.

• Pete did worse than about 73% of the test takers.

• Pete did better than about 63% of the test takers.

• Pete did better than about 73% of the test takers.

The density curve shown models the distribution of a quantitative variable that is equally likely to take any value in the interval from 0 to 2. What percent of the observations lie between 0.5 and 1.2?

• 25%

• 35%

• 50%

• 70%

Which of the following is closest to the 28th percentile of the standard normal distribution?

• z=-0.58

• z=-0.50

• z=0.39

• z=0.61

For this normal distribution, the standard deviation is closest to:

• 1

• 2

• 3

• 6

Scores on the ACT college entrance exam can be modeled using a normal distribution with mean 21 and standard deviation 5. Wayne’s standardized score on the ACT was -0.6. What was Wayne’s actual ACT score?

• 3

• 13

• 16

• 18

The Environmental Protection Agency (EPA) requires that the exhaust from each model of motor vehicle be tested for the level of several pollutants. The level of oxides of nitrogen (NOX) in the exhaust of one light truck model was found to vary among individual trucks according to an approximately normal distribution with mean = 1.50 grams per mile drive and standard deviation = 0.25 gram per mile. Which of the following best estimates the percent of light trucks of this model with NOX levels greater than 2 grams per mile?

• 2.5%

• 5%

• 16%

• 32%

The figure shows a density curve that models the distribution of a quantitative variable. Seven values are marked on the density curve. Which of the following statements is true?

• The mean of the distribution is E.

• The median of the distribution is C.

• The third quartile of the distribution is D.

• The area under the curve between A and G is 1.

A species of cockroach has weights that are approximately normally distributed with a mean of 50 grams. After measuring the weights of many of these cockroaches, a lab assistant reports that 14% of the cockroaches weigh more than 55 grams. Based on this report, what is the approximate standard deviation of weight for this species of cockroaches?

• 4.6

• 5.0

• 6.2

• 14.0

In 1965, the mean price of a new car was $2650 and the standard deviation was $1000. In 2019, the mean was $36,700 and the standard deviation was $9000. If a Ford Mustang cost $2300 in 1965 and $34,000 in 2019, in which year was it more expensive relative to other cars?

• 1965, because the standardized score is greater than in 2019.

• 1965, because the standard deviation is smaller.

• 2019, because the standardized score is greater than in 1965.

• 2019, because $34,000 is greater than $2300.

The distribution of the time it takes for different people to solve a certain crossword puzzle is strongly skewed to the right with a mean of 30 minutes and a standard deviation of 15 minutes. The distribution of z-scores for those times is

• normally distributed with mean 30 and SD 15.

• skewed to the right with mean 30 and SD 15.

• normally distributed with mean 0 and SD 1.

• skewed to the right with mean 0 and SD 1.