STAT303 Sec 508-510Fall 2010Exam #1Form AInstructor: Julie Hagen CarrollName:1. Don’t even open this until you are told to do so.2. All graphs are on the last page which you may remove.3. There are 20 multiple-choice questions on this exam, each worth 5 points. There is partial credit. Please mark youranswers clearly. Multiple marks will be counted wrong.4. You will have 60 minutes to finish this exam.5. If you have questions, please write out what you are thinking on the back of the page so that we can discuss it afterI return it to you.6. If you are caught cheating or helping someone to cheat on this exam, you both will receive a grade of zero on theexam. You must work alone.7. This exam is worth the same as a regular exam (this may differ from section to section.8. When you are finished please make sure you have marked your CORRECT section (Tuesday 12:45 is 508, 2:20 is 509,and 3:55 is 510) and FORM and 20 answers, then turn in JUST your scantron.9. Good luck!1STAT303 sec 508-510 Exam #1, Form A Fall 20101. Which of the following best describes a 95thpercentilefor a given distribution?A. the value of 95% of the observationsB. a number that is 2 standard deviations above themean of the distributionC. a number that would be equivalent to 95 on a 100point scaleD. a number such that 95% percent of the observa-tions in the distribution have that value or lessE. Two of the above are true.2. Bubba and Joe Bob decide they want to shoot Mrs.Cleary’s scarecrow. They each take three shots. Bubbahits both the right and the left arm and the stomach.Joe Bob hits the left knee all three times. They wereboth aiming for the heart. Which of the following istrue?A. Bubba is unbiased but has high variability.B. Joe Bob is unbiased but has high variability.C. Bubba is biased but has low variability.D. Joe Bob is biased but has high variability.E. None of the above are correct.3. Suppose x = 5 and sx= 2. What is y and syif y =3x − 4?A. y = 15 and sy= 6B. y = 15 and sy= 2C.y = 11 and sy= 10D. y = 11 and sy= 2E. y = 11 and sy= 64. Explain the boxplot for Truck.A. There are only 5 observations.B. x = ˜xC. the data is normal since there is an outlier on bothendsD. Q3= ˜x = Q1E. Q3= ˜x or ˜x = Q15. For X ∼ N(3, 22), what is P (X > 0.65)? (rounded)A. 0.88B. 0.74C. 0.64D. 0.26E. 0.126. For a certain dataset, you are told that the standarddeviation, s = 0. What else can you say about thedataset?A. the mean, x = 0B. the median, ˜x = 0C. the IQR = 0D. all of the aboveE. none of the above7. If the 5-Number-Summaries for a dataset are: 22, 37,52, 65, 79, which of the following best describes thedistribution?A. skewed leftB. skewed rightC. skewed right with outliersD. normalE. uniform8. Some companies “grade on a bell curve” to compare theperformance of their managers and professional work-ers. This forces the use of some low performance rat-ings, so that not all workers are graded “above aver-age”. Until the threat of lawsuits forced a change, FordMotor Company’s “performance management process”assigned 15% A’s and C’s and 70% B’s to the company’s18,000 managers. Assuming the distribution is approx-imately bell-shaped (normal) what are the approximatemean and standard deviation if C’s have scores of 25 orless and A’s have scores of 475 or more?A. x = 200 and s = 175B. x = 200 and s = 275C. x = 250 and s = 225D. x = 200 and s = 225E. x = 225 and s = 2009. Which of the following statements is/are true?A. The value of the median will change if you add 10to the maximum in a dataset.B. The IQR covers 50% of the range (spread) of thedata.C. A z-score tells us how many standard deviationsan observation is from its mean.D. All of the above are true statements.E. Exactly two of the above are true statements (ex-cluding D.).10. What is z∗such that P (Z > z∗) = 0.075 and Z ∼N(0, 12)?A. 0.53B. −1.44C. 0.47D. 1.44E. 0.77342STAT303 sec 508-510 Exam #1, Form A Fall 201011. If the difference in the average husbands’ and wives’weights is H − W ∼ N (25, 102), how likely is the wifeto weigh more than the husband?A. You need to know the average couples’ weight.B. −2.5C. 0.0062D. 0.9938E. 0.2512. If we know that a distribution is skewed to the right,which of the following is true?A. The mean is smaller than the median.B. Outliers would most likely be to the left.C. The histogram would be shorter on the left.D. All of the above are true.E. None of the above are true.13. Numbering the boxplots 1 through 4 from left to right,which distribution is approximately uniform?A. You can’t tell by looking at a boxplot.B. 3 only since it’s the most spread out.C. 4 only since it’s the most symmetric.D. Both 3 and 4 are uniform.E. None of the boxplots are uniform.14. Which boxplot has an Interquartile Range, IQR, ofabout 20?A. 1B. 2C. 3D. 4E. 1,2 and 4 are all the same.15. Suppose the average height of the American male is5”10’ or 70 inches with a standard deviation of 6 inches.What is the distribution of a sample 50 Americanmales’ heights?A. N(70, 62)B. N(70, (6/√50)2)C. µ = 70 and σ = 6, but we can’t say the shape isnormalD. µ = 70 and σ = 6/√50, but we can’t say the shapeis normalE. Not enough information is given.16. IF the heights of American males is X ∼ N(70, 62), howlikely are you to find an American male over 7 feet, 84inches?A. 0.0099B. 0.9901C. 0 (z-score is huge)D. 1 (z-score is huge)E. more than half the time17. Suppose you know that a distribution is bell-shaped,with mean, x = 30 and standard deviation, sx= 4.Approximately what percent of the data will fall be-tween 22 and 34?A. about 95%B. between 50 and 68%C. about 80%D. between 95 and 100%E. about 75%18. What is z∗such that P (−z∗< Z < z∗) = 0.75 andZ ∼ N(0, 12)A. 0.675B. 1.15C. 0.7734D. 0.75E. 1.7519. Suppose your high school grading system used an 8point scale with a mean of 6.5 and a standard deviationof 1.2 and your average was 7. What is your equivalentaverage in a 100 point system with a mean of 82 and astandard deviation of 14?A. 82.417B. 87.838C. 76.162D. 81.583E. 83.220. Suppose you get a z-score = 1.2 on this exam. Question#10 is really hard, so I decide to give everyone credit,i.e., I give 5 points to everyone who missed it. WhatSHOULD you think about this if you got the problemright originally?A. It doesn’t matter since your z-score would stay thesame.B. You get gypped since your z-score would decrease.C. You benefit since your z-score would increase.D. Your z-score
View Full Document
Unlocking...