Midterm-1-B-Answers

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Jan 9, 2024

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Name: Student ID: STAT 121, Midterm-1, Version B Completely fill in the appropriate bubble on the bubble sheet provided, and also circle your answer choices on this test sheet. Your name, student ID and midterm version (A or B) should also be bubbled-in on the bubble sheet. Alphabetical part of the student ID should be entered first. Please return both the midterm sheet and the bubble sheet. Each question is worth 1 point. Due to rounding, some of your answers could be slightly different from the choices given. Please select the closest answer. 1. Discrete or continuous? The number of patients who reported that a new drug had relieved their pain A. Discrete B. Continuous 2. A firm is interested in estimating the average per capita household income in a certain city. The city is divided into 60 blocks, and the researchers decided to take a simple random sample of 250 households from each of the 60 blocks, and obtain income data from the households in the sample. What kind of sample is this? A. Simple random sample B. Cluster sample C. Voluntary response D. Systematic sample E. Stratified sample 3. The superintendent of a large school district wants to test the effectiveness of a new program designed to improve reading skills among elementary school children. There are 30 elementary schools in the district. The superintendent chooses a simple random sample of five schools, and institutes the new reading program for all the students in those five schools. A total of 4700 children attend these five schools. What kind of sample is this? A. Simple random B. Stratified sample C. Voluntary response D. Cluster sample E. Systematic sample 4. Size of soft-drink ordered at a fast food restaurant comes in three sizes: small, medium or large. What type of variable is this? A. Nominal B. Continuous C. Ordinal 5. A medical researcher wants to determine whether exercising can lower blood pressure. She measures the blood pressure of 100 individuals present at a health fair, and interviews them about their exercise habits. She divides the individuals into two

categories: those whose typical level of exercise is low, and those whose level of exercise is high. This study is a A. Observational study B. Randomized experiment 6. For the study mentioned in Question 5, it was noted that the subjects in the low-exercise group had considerably higher blood pressure, on the average, than subjects in the high- exercise group. The researcher concludes that exercise decreases blood pressure. Is this conclusion justified? Choose from the following two options: A. The conclusion that exercise decreases blood pressure may not be justified since there could be confounding factors B. The conclusion that exercise decreases blood pressure is justified 7. In a study to be conducted at the University of Southern California, researchers will study elementary school students in 12 California communities. They plan to measure the respiratory function of the children, and the levels of air pollution in the communities each year, for 10 years. This study is a A. Cross-sectional study B. Prospective study C. Retrospective study (For Questions 8 and 9). Forty rats were trained to run a maze. The following histogram presents the numbers of trials it took each rat to learn the maze. 8. How many rats took 8 trials or more to learn the maze? A. 18 B. 19 C. 1 D. 5 E. 3 9. The histogram is A. Bell-shaped B. Symmetric C. Skewed to the right D. Skewed to the left

(For questions 10 and 11): The following frequency distribution represents the batting averages of 200 Major League Baseball players who had three hundred or more plate appearances during a recent season: Batting Average Frequency 0.180 – 0.199 4 0.200 – 0.219 10 0.220 – 0.239 35 0.240 – 0.259 45 0.260 – 0.279 39 0.280 – 0.299 37 0.300 – 0.319 21 0.320 – 0.339 8 0.340 – 0.359 1 10. What is the class width? A. 0.020 B. 0.019 C. 0.179 D. 0.160 11. What percentage of players had batting averages of 0.260 or more? A. 24.5% B. 75.5% C. 53% D. 17.5% E. 49% 12. Determine the mean and median for the following relative frequency histogram from the given choices: A. Mean = 4.6; Median = 5 B. Mean = 4.5; Median = 4.2 C. Mean = 3.5; Median = 4.3 D. Mean = 6.1; Median = 6 13. According to a survey, the mean personal income for a group of adults is $38,300. A histogram for incomes is skewed to the right. Which of the following is a possible value for the median income? A. $38,000 B. $40,000 C . $50,000 D. $26,000 E. Can’t be determined from the given information

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(For Questions 14 – 16). Consider the following data consisting of 16 numbers, sorted from the smallest to the largest: 3, 7, 9, 11, 13, 15, 19, 21, 22, 28, 29, 35, 37, 39, 41, 78 14. The median of the data is A. 21 B. 22 C. 21.5 D. 21 and 22 15. The first and third quartiles are A. Q1 = 11, Q3 = 37 B. Q1 = 12, Q3 = 37 C. Q1 = 11, Q3 = 36 D. Q1 = 12, Q3 = 36 16. The outliers are A. the number 3 B. the number 78 C. the numbers 3 and 78 D. there are no outliers ( For questions 17 and 18). A study conducted by the Center for Population Economics at the University of Chicago studied the birth weights of 621 babies born in New York. The mean weight was 3234 grams with a standard deviation of 871 grams. It is also known that the birthweight data were approximately bell-shaped. 17. Approximately what percentage of the newborns weighed between 2363 grams and 4105 grams? A. 68% B. 95% C. Almost 100 % D. Can't be determined from the given information 18. Approximately what percentage of the newborns weighed less than 1492 grams? A. 68% B. 97.5% C. 95% D. 2.5% E. Can't be determined from the given information (For questions 19 – 22). The wingspan X (in mm) and the lifespan Y (in days) were measured for 22 species of butterfly. The results are: 𝑋𝑋 � = 28.31, 𝑌𝑌 � = 31.10, S X = 3.53, S Y = 7.22, Correlation = r = – 0.91 19. The slope and intercept of the regression line are A. Slope = – 1.86, Intercept = 83.76 B. Slope = 1.92, Intercept = – 23.26 C. Slope = 1.86, Intercept = –21.56 D. Slope = – 1.92, Intercept = 85 20. Predict the lifespan of a butterfly when the wingspan is 31 millimeters A. 25.94 days B. 26.10 days C. 36.10 days D. 36.26 days

21. The correlation r = – 0.91 between the lifespan and the wingspan tells us that A. For every additional 1 millimeter for the wingspan, the lifespan decreases by 0.91 days B. As the wingspan decreases, the lifespan tends to decrease C. As the wingspan increases, the lifespan tends to decrease D. The correlation being negative, there is no linear association between lifespan and wingspan 22. Suppose the wingspan of two butterflies differ by 3 millimeters. How much would we expect their lifespans to differ? A. 5.76 days B. 2.82 days C. 3 days D. 5.58 days E. 2.73 days (For Questions 23–25). Two drugs, Telmisartan and Ramipril, are to be compared for their effectiveness to reduce cardiac events. The following table presents the numbers of patients who experienced fatal heart attack, non-fatal heart attack, or no heart attack while being on the drugs for a certain period of time. 23. Among those taking Ramipril, what percentage had fatal heart attacks? A. 50.2% B. 0.502% C. 7% D. 3.5% 24. Among those taking Telmisartan, what percentage had fatal heart attacks? A. 0.498% B. 3.5% C. 49.8% D. 7% 25. Is the occurrence of a fatal heart attack independent of the drug? Why or why not? A. No, since the % of a fatal heart attack are very different for the two drugs B. Yes, since the % of a fatal heart attack are nearly the same for the two drugs Fatal heart attack Non–fatal Heart attack No heart attack Total Telmisartan 598 431 7513 8542 Ramipril 603 400 7573 8576 Total 1201 831 15086

Midterm-1-B-Answers

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