AP Stats Random Variables Practice

A simple random sample of 25 world-ranked tennis players provides the following statistics: Number of hours practiced per day: mean = 7.3, standard deviation = 1.2 Yearly winnings: mean = $1,820,000, standard deviation = $310,000 Correlation = 0.23 Based on this data, what is the LSRL that predicts winnings from number of hours practiced?

Which of the following statements about the correlation (r) are true?

• I only

• II only

• III only

• I, II, and III

• All are false.

Answer explanation

None of the statements are true.

I. r = 0 means there's no linear relationship, not no relationship.

II. r is never measured as a percent.

III. correlation doesn't prove causation.

A study is conducted relating AP Statistics exam scores to the total number of study hours for the AP Statistics class put in by students during the academic year, and the correlation is found to be 0.6. Which of the following are true statements?

• III only

• I and II

• I and III

• II and III

• I, II, and III

Which of the following are true statements about the correlation coefficient?

• I and II

• I and III

• II and III

• I, II, and III

• I or II

Answer explanation

Correlation is unitless, so changing measurements or changing which variable is x and which is y will not change correlation.

Correlation is greatly affected by outliers.

Which of the following statements about residuals are true?

• I and II

• I and III

• II and III

• I, II, and III

• None are true.

Answer explanation

Name the sampling method:

Assign each car in a dealership a number and then use a random-number table to select the cars to be inspected.

• systematic

• simple random sample

• convenience

• Self - selected (volunteer)

The boxplots above summarize two data sets, A and B.

Which of the following must be true?

 

I. Set A contains more data than Set B.

II. The box of Set A contains more data than the box of Set B.

III. The data in Set A have a larger range than the data in Set B.

• I only

• III only

• I and II only

• II and III only

• I, II, and III

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

• 8

• 10

• 16

• 40

• 50

The histogram below 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?

• 2.5

• 7.25

• 12.25

• 15

• 17.50

The histogram above shows the number of minutes needed by 45 students to finish playing a computer game.

Which of the following statements is correct?

• The distribution is skewed to the right.

• The distribution is skewed to the left.

• The distribution appears to be normal.

• The distribution appears to be chi-square.

• The distribution appears to be uniform.