AP Stats: Midterm Review Exam Complete Questions And Correct Detailed Answers.

D - correct answer A forester studying oak trees finds that the correlation between x= the age (measured in years) and y= height (in feet) of a sample of trees is 0.78. Which of the following statements must be true? a) 78% of the variability in tree heights can be explained by variation on the trees' ages. b) for every year a tree ages, its height increases on average by 78%. c) if we let x= height of trees and y= age of trees, then the correlation would be the reciprocal of 0.78. d) if we measure the height in meters instead of feet, the correlation would still be 0.78. e) the unit for correlation in this context is foot-years. D - correct answer One flight---Philadelphia to West Palm Beach, FL ---is 953 miles long and costs $110. Which of the following expressions correctly represents the residual for this data point? a) 101.24+0.02977 * 953 b) 953-(101.24+ 0.02977 * 110) c) (101.24 + 0.02977 * 110) - 953 d) 110- (101.24 + 0.02977 * 953) e) (101.24 + 0.02977 * 953) - 110 C - correct answer Which of the following best describes what S=20.7237 measures? a) the standard deviation of air fares b) the standard deviation of flight distances c) the standard deviation of the residuals d) the slope of the least squares regression line e) the standard deviation of the slope A - correct answer The unusual point in the upper left part of the plot is for navy beans, with 15.8 grams of protein and 15.8 grams of carbohydrates. Which of the following best describes how correlation would change if we removed navy beans from the data set? a) the correlation would be closer to 1, because the remaining data would have a stronger positive relationship. b) the correlation would be closer to 1, because there would be fewer individuals in the data set. c) the correlation would be closer to 0, because the data would more closely resemble a straight line. d) the correlation would be closer to 0, because the standard deviation of the residuals would be smaller. e) correlation would no longer be calculated, because the remaining data would fall into two distinct groups. A - correct answer The protein content for the 15 bean varieties has a mean of 12.2 grams and a standard deviation of 5.3 grams. The mean carbohydrate content is 33.6 grams with a standard deviation of 15.7 grams. The correlation is 0.84. Which of the following expressions represents the slope of the least squares regression of y= protein content on x= carbohydrate content? a) (0.84)(5.3)/(15.7) b) (0.84)(15.7)/(5.3) c) (0.84)(12.2)/(33.6) d) (0.84)(33.6)/(12.2) e) (33.6)/(0.84)(12.2) C - correct answer The least squares regression line minimizes which of the following quantities? a) the sum of the squared differences between the observed values of the response variable and the mean of the response variable b) the sum of the squared differences between the observed values of the explanatory variable and the mean of the explanatory variable c) the sum of the squared differences between the observed values of the response variable and the predicted values of the response variable d) the sum of the squared differences between the observed values of the explanatory variable and the predicted values of the explanatory variable e) the sum of the squared differences between the predicted values of the explanatory variable and the mean of the explanatory variable C - correct answer A recent investigation of prices for five-year-old Toyota Camrys in Montgomery, Alabama, and New York, New York, revealed that the mean price in Montgomery was $13,200 with a standard deviation of $1000. In New York, the mean price was $12,800 with a standard deviation of $1800. Which of the following statements is true? a) a car priced at $13,000 would have a negative standard score in both cities. b) the standard score of a car priced at $10,000 would be lower in New York than in Montgomery c) the standard score for a car priced at $15,000 would be higher in Montgomery than in New York. d) a car with a standardized score of 0 in Montgomery would have a negative standard score in New York e) a car with a standardized score of 0 in New York would also have a standardized score of 0 in Montgomery. B - correct answer All of the following small data sets have a mean of 5. Which one has the lowest standard deviation? a) 1 1 5 5 5 9 9 b) 1 3 5 5 5 7 9 c) 1 1 5 9 9 d) 1 3 5 7 9 e) 1 1 9 9 E - correct answer The five-number summary of the weights (in grams) of 1200 tomatoes grown in a certain greenhouse was 90 113.. How many tomatoes weighed less than 161 grams? a) 140 b) 236 c) 300 d) 600 e) 900 D - correct answer The same 1200 tomatoes from question #9 have a mean weight of 143 grams and a standard deviation of 35 grams. If the weights are Normally distributed, approximately how many tomatoes weigh between 73 grams and 178 grams? a) 384 b) 600 c) 816 d) 978 e) 1140 D - correct answer A political action committee sends out a questionnaire to randomly selected mailing addresses, asking people to rate the importance of a variety of economic and social issues facing the country. At the end of the questionnaire is an (optional) invitation to donate money to the organization. Which of the following statements about this survey is true? a) the survey results are invalid because it's impossible to word questions about politics without creating bias. b) the survey results are invalid because only surveys conducted by phone are free from bias. c) the survey results will underestimate support for this political action committee in the entire population because people who respond are