Stat220 Midterm Nov 8, 2006Name (print):Section:This is the midterm for Stat220. It covers chapters 1-5, 8-11 and 19, plus the corresponding lec-tures. There are 5 questions f or a total of 65 points. You have about 50 minutes to work on it. Anormal table is prov ided on the last page, and you can use the back side of that page as scratchpaper.Exam rules:1. You must keep the exam closed and are not allowed to write until it is announcedthat you can start the exam.2. This is a closed book exam, and no notes are allowed.3. You may use a calculator. Cell phones may not be used .4. Just like in the homeworks, you won’t get points for an answer without explanation. So makesure to show your work, and explain all your answers, u nless it is explicitly s tated that youdon’t have to do so.5. Write your name and s ection on the exam, and sign the honor statement below, certifyingthat the exam is completely your own work.6. Code of conduct: you must do th is exam completely by yourself. Students su sp ected ofcheating or dishonest practices will be reported to the Vice President of Student Affairs. Suchpractices include, but are not limited to (i) making use of books, notes, or other material, (ii)communicating with other students in any way, (iii) looking at the work of other students,and (iv) purposely exposing written papers to the view of other students.Good luck!!Honor statement: I certify that this exam is completely my own work, and that I followed theco de of conduct as outlined in point 6 above.Signature:Q1 (10 pt) Q2 (15 pt) Q3 (10 pt) Q4 (10 pt) Q5 (20 p t) Total (65 p t)1 of 8Stat220 Midterm Nov 8, 20061. C alifornia is evaluating a new program to rehabilitate prisoners before their release. The objectis to reduce the “recidivism rate” – the percentage who will be back in prison within two yearsof release. The program involves several months of “boot camp” – a m ilitary-style basic trainingwith very strict discipline. Admission to the program is voluntary. It was found that inmateswho completed boot camp were less likely to return to prison than other inmates.(a)(2) What is the treatment group? What is the control group?(b)(3) Is this an observational study or a randomized experiment? Explain your answer.(c)(5) True or false: the data show that the boot camp reduced recidivism. Explain briefly.2 of 8Stat220 Midterm Nov 8, 20062. In each of the following statements, circle any and all options that apply (so you can circlemore than one). You do NOT need to explain your choices.(a)(3) The following methods are probability sampling methods:simple random samp ling / convenience sampling / quota samp ling / cluster sampling(b)(3) A histogram always balances when supported at its:average / median / standard deviation / 75th percentile / none of these(c)(3) When the r.m.s. size of a list is zero, then all entries must be:equal to each other / equal to zero / none of these(d)(3) When all entries in a list are multiplied by 2, which of the following change?average / median / standard deviation / standard units / none of these(e)(3) When a constant is added to all entries in a list, which of the following change?average / median / standard deviation / standard units / none of these3 of 8Stat220 Midterm Nov 8, 20063. T he figure below is a histogram for the blood pressu res of subj ects in a certain stu dy. Theaverage was 122 mm, and the SD was 12.(I’ll put in the plot that’s on page 108 of the solutionmanual)(a)(5) Use the normal approximation to estimate the percentage of people with blood pressuresbetween 120 mm and 130 mm.4 of 8Stat220 Midterm Nov 8, 2006(b)(5) The estimate found in part (a) is a bit ......Fill in the blank. Options: too high, too low. E xplain your choice. You don’t have to doany computations.5 of 8Stat220 Midterm Nov 8, 20064. In a study of a representative group of men, the correlation between height and weight was0.43. The scatter diagram was football shaped.(a)(5) Sketch a scatter diagram: draw and label the axes (take weight as the dependent variable),draw the fo otball, draw and label the SD line, and draw an d label the regression line forweight on height.(b)(5) One man in the study was both one SD above average in height and one SD above averagein weight. His weight was(i) larger than(ii) smaller than(iii) equal tothe average weight of all men of his height in the stud y. Explain your choice.6 of 8Stat220 Midterm Nov 8, 20065. A statistical analysis was made of the midterm and final scores in a large course, with thefollowing results:Midterm score: Average = 65, SD = 25,Final score: Average = 60, SD = 15,r = 0.6The scatter diagram was football-shaped. For each student, the final score was predicted fromthe midterm score using the regression line.(a)(5) For about 1/3 of the students, the prediction for the final score was off by more than .....points. Fill in the blank. Options: 6, 9, 12, 15, 16, 20, 25. Explain your choice.(b)(5) Predict the final score for a student whose midterm score was 80.This question continues on the next page.7 of 8Stat220 Midterm Nov 8, 2006(c)(5) The prediction of part (b) is likely to be off by ..... points or so. Fill in the blank. Options:6, 9, 12, 15, 16, 20, 25. Explain your choice.(d)(5) Of the students who scored 80 on the midterm, about what percentage scored over 80 onthe final?8 of