Math 140G: Test #1 Fall 2008 Page 1 of 6 Math 140: Statistics Your Name ______________________ Test 1,September 24, 2008 1. (6 pts.) Fill-in-the-blank: a. In a(n) ____________________ experiment, subjects do not know whether they are in the treatment or control group. Neither do the evaluators. b. If the study compares the records of patients receiving a treatment to the records of previous patients that did not receive the treatment, the study is said to use _________________________. c. ____________________ means a difference between the treatment and control groups, other than the treatment, which affects the responses being studied. 2. (6 pts.) To improve physical fitness, a school adopts an opt-in fitness program. Students are assigned to two groups. One group will spend extra time exercising, one won’t. a. Is this a controlled or observational study? b. Identify the two groups in the study. c. If data shows a general improvement in fitness, could you conclude the program was beneficial? Justify your conclusion. 3. (4 pts.) (Hypothetical) In a study of a new surgical protocol in 1975, there were 700 deaths per 10,000 patients treated. By 2000, the death rate had dropped to 250 deaths per 10,000 treated. True or false, and explain: the safety of this surgical protocol improved from 1975 to 2000. 4. (6 pts.) Recall that you can convert form pounds to kilograms by dividing by 2.20. If the average weight of 20 students is found to be 160 pounds with a standard deviation of 20, what will be the average and standard deviation when converted to kilograms?Math 140G: Test #1 Fall 2008 Page 2 of 6 5. (10 pts.) Use this scatter diagram to answer the questions that follow: a) Add the point (1.5, 2.5) to the diagram. b) When x is 2, what is y? c) Is the average for x closer to 1, 2.5, or 3.5? d) Is the standard deviation for x closer to 0.25, 0.75, or 1.5? e) Describe the correlation (strong, weak, positive, negative) between the x-data and the y-data. 6. (4 pts.) In a statistic class, the first quiz had an average score of 75 with an SD of 15. The second quiz had an average score of 70 and an SD of 4. On which quiz would you expect more scores of 60 or less? Why?Math 140G: Test #1 Fall 2008 Page 3 of 6 7. (2 pts.) For this histogram, which would you expect to be smaller, the mean or the median? 8. (12 pts) Assume Interim is graded Honors, Pass, Fail where: 90 to 100 Honors 70 to 90 Pass 0 to 70 Fail Here are the grades for 20 students in a class: 88, 72, 64, 91, 65, 90, 88, 73, 81, 95, 86, 76, 69, 77, 83, 79, 81, 74, 17, 100 Create a histogram for this data using the three categories described above. Be sure to carefully and fully label your histogram.Math 140G: Test #1 Fall 2008 Page 4 of 6 9. (9 pts.) Find the area under the normal curve: a) to the left of 0.8 b) to the left of –1.4 c) between –1.0 and 1.15 10. (9 pts.) On the admission test, applicants averaged about 85 with an SD of 4. a) What percentage of applicants scored between 81 and 89? b) What percentage of men scored above 93? c) What percentage of men scored below 80?Math 140G: Test #1 Fall 2008 Page 5 of 6 11. (10 pts.) Use this percentile table to answer the questions that follow: Percent Income 1 $0 10 $18,000 25 $39,000 50 $84,000 75 $125,000 90 $185,000 99 $630,000 a) What is the percentage of incomes between $84,000, and $185,000? b) The least prosperous 25% have an income below what amount? c) What percentile rank would a person with an income of $125,000 have? d) What is the interquartile range for this data? e) If a college applicant needs an income of less than $50,000 to qualify for financial add, estimate the percentage of people that would qualify? 12. (8 pts.) Applicants have an average Math SAT score of 535 with a SD of 100. a) An applicant scored 750. She was at the _____ percentile of the score distribution. b) Estimate the 80th percentile rank for the Math SAT scores.Math 140G: Test #1 Fall 2008 Page 6 of 6 13. Use the following table to answer the following: x y 1 1 1 2 1 1 1 3 2 1 2 4 2 1 3 2 3 2 4 3 a) (6 pts.) Find the average and standard deviation for both x and y. Be sure to identify each answer. b) (8 pts.) Find the correlation coefficient for this data. Please show relevant work. (Feel free to write in the open area of the table.) c) (2 pts.) Based on the correlation coefficient you calculate, describe how the x and y data are related. Pledged: