AP Practice MC

A random sample of 374 United States pennies was collected, and the age of each penny was determined. According to the boxplot shown, what is the approximate IQR of the ages?

• 8

• 10

• 16

• 40

• 50

The weight of adult male grizzly bears living in the wild in the continental United States is approximately normally distributed with a mean of 500 pounds and a standard deviation of 50 pounds. The weight of adult female grizzly bears is approximately normally distributed with a mean of 300 pounds and a standard deviation of 40 pounds. Approximately, what would be the weight of a female grizzly bear with the same standardized score (z-score) as a male grizzly bear with a weight of 530 pounds?

• 276 pounds

• 324 pounds

• 330 pounds

• 340 pounds

• 530 pounds

The commuting time for a student to travel from home to a college campus is normally distributed with a mean of 30 minutes and a standard deviation of 5 minutes. If the student leaves home at 8:25 am, what is the probability that the student will arrive at the college campus later than 9 am?

• 0.16

• 0.32

• 0.50

• 0.84

• 1.00

The boxplots shown summarize two data sets, I and II. Based on the boxplots, which of the following statements about these two data sets CANNOT be justified?

• The range of data set I is equal to the range of data set II

• The interquartile range of data set I is equal to the interquartile range of data set II

• The median of data set I is less than the median of data set II

• Data set I and data set II have the same number of data points

• About 75% of the values in data set II are greater than or equal to about 50% of the values in data set I.

The least squares regression line was fitted to the weights (in pounds) versus age (in months) of a group of many young children. The equation of the line is shown on the left, where y-hat is the predicted weight and t is the age of the child.  A 20-month old child in this group has an actual weight of 25 pounds.  Which of the following is the residual weight, in  pounds, for this child?

• -7.85

• -4.60

• 4.60

• 5.00

• 7.85

Each of 100 laboratory rats has available both plain water and a mixture of water and caffeine in their cages. After 24 hours, two measures were recorded for each rat: the amount of caffeine the rat consumed, X, and the rat's blood pressure, Y. The correlation between X and Y was 0.428. Which of the following conclusions is justified on the basis of this study?

• The correlation between X and Y in the population of rats is also 0.428

• If the rats stop drinking the water/caffeine mixture, this would cause a reduction in their blood pressure.

• About 18% of the variation in blood pressure can be explained by a linear relationship between blood pressure and caffeine consumed

• Rats with lower blood pressure do not like water/caffeine mixture as much as do rats with higher blood pressure.

• Since the correlation is not very high, the relationship between the amount of caffeine consumed and blood pressure is not linear.

A complex electronic device contains three components, A, B, C. The probabilities of failure for each component in one year are 0.01, 0.03, 0.04, respectively. If any one component fails, the device will fail. If the components fail independently of one another, what is the probability that the device will NOT fail in one year?

• Less than 0.01

• 0.078

• 0.080

• 0.922

• Greater than 0.99

The histogram pictured here displays the frequencies of waiting times, in minutes, for 175 patients in a dentist's office.

Which of the following could be the median of the waiting times, in minutes?

• 2.50

• 7.25

• 12.25

• 15.00

• 17.50

Blocking is a technique that can be used to filter out the effects of extraneous (confounding) factors.

• True

• False

A study is an observational study if the investigator observes the behavior of a response variable when one or more factors are manipulated.

• True

• False

Answer explanation

In an observational study nothing is manipulated (changed or imposed).