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TAMU STAT 303 - ex1asp11

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STAT303 Sec 508-510Spring 2011Exam #1Form AInstructor: Julie Hagen CarrollName:1. Don’t even open this until you are told to do so.2. 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.3. You will have 60 minutes to finish this exam.4. If you have questions, please write out what you are thinking on the back of the page so that we can discuss it after Ireturn it to you.5. If you are caught cheating or helping someone to cheat on this exam, you both will receive a grade of zero on the exam.You must work alone.6. This exam is worth the same as a regular exam (this may differ from section to section.7. 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.8. Good luck!1STAT303 sec 508-510 Exam #1, Form A Spring 20111. If each of 25 observations was multiplied by 10, which ofthe following would be true?A. The mean and the standard deviation would be 10times larger.B. The median and the IQR would be the same as be-fore (not affected).C. The z-score would be 10 times larger.D. All of the above would be true.E. Two of the above would be true.2. If X25∼ N(5, 102), what is P (X25< 8.75)?A. 0.9699B. 0.1875C. 0.9999D. 0.648E. 0.3753. In the histogram above, the bin represents the value tothe left and only that value. Which of the following is/aretrue?A. The median is 17 because it is the tallest bin.B. The median is greater than (to the right of) themean because the distribution is skewed to the right.C. The median and standard deviation should be usedto describe this distribution because it is skewed.D. All of the above are true.E. None of the above are true.4. The 5 Number Summary for the previous histogram isA. 10,15,17,17,20B. 11,15,17,17,20C. 11,15,17,17,19D. 12,15,17,17,20E. 12,15,17,17,195. Still talking about the histogram, what would happen ifthe minimum value was decreased, i.e., we substracted10 from the minimum?A. The mean would be shifted down by 10 but the stan-dard deviation would stay the same.B. Both the mean and the standard deviation wouldbe smaller by 10.C. The mean would be smaller but the standard devi-ation would be larger.D. Both the mean and the standard deviation wouldbe smaller but we don’t know by how much.E. None of the above are totally correct.6. What is z∗such that P (−z∗< Z < z∗) = 0.55 andZ ∼ N (0, 12)A. 0.7088B. 0.6736C. 0.13D. 0.755E. 0.5897. Suppose your high school grading system used an 8 pointscale with a mean of 6.5 and a standard deviation of 1.2and your average was 7. What is your equivalent averagein a 100 point system with a mean of 82 and a standarddeviation of 14?A. 82.417B. 87.838C. 76.162D. 81.583E. 83.28. A boxplot is useful forA. determining the shape of a distribution.B. determining whether there are outliers in thedataset.C. determining precisely what the sample mean is.D. A. and B. are correct.E. A., B. and C. are all correct.9. What does it mean to have a z-score of 1.5 on this exam?A. It means you’re in the upper 10 almost 5%.B. It means you only missed 1.5 points.C. It means your grade is 1.5 times the average.D. It means you made the 75thpercentile becauseyou’re halfway between the mean, 0, and the maxi-mum, 3.E. None of the above are correct.10. If we have a standard normal distribution what is theproportion of values between z = −1.56 and z = −2.05?Drawing a picture may help.A. −0.0392B. 0.0392C. 0.0796D. 0.0594E. 0.02022STAT303 sec 508-510 Exam #1, Form A Spring 201111. Which parts of a sampling distribution does the size of asample, n, affect?A. the shapeB. the centerC. the spreadD. all of the aboveE. only two of the aboveBox n Mean Std.Dev. Median Min Max Q1 Q31 50 16.04 1.979 16 11 19 15 182 50 15.98 1.720 16 13 19 15 173 50 16.22 1.866 17 11 19 15 1712. Labelling the boxplots A, B, C, which is the correct or-dering?A. 1=A, 2=B, 3=CB. 1=B, 2=C, 3=AC. 1=C, 2=B, 3=AD. 1=C, 2=A, 3=BE. 1=A, 2=C, 3=B13. Why is it important to know if there are outliers in adataset?A. They determine(affect) which statistics are appro-priate.B. We can only use z-scores since they are the onlystatistics we’ve discussed that aren’t affected by out-liers.C. We can’t use z-scores since the distribution is notnormal (it’s skewed).D. Two of the above are correct.E. None of the above are correct.14. During the stockmarket boom of the 1990s, initial publicofferings (IPOs) of the stock of new companies often pro-duced enormous gains for people who bought the stockswhen they first became available. At least that’s whatlegend says. A study of all 4567 companies that wentpublic in the years 1990 to 2000 (excluding very smallIPOs) found that on the average their stock prices hadeither risen 111% or declined 31% by the end of the 2000.One of these numbers is the mean change in price and theother is the median change. Which is which and why?Think about what the distribution should look like.A. These calculations must be wrong since one is pos-itive and the other is negative.B. The mean is 111% and the median is 31% since thedata is obviously skewed to the left (more did well).C. The median is 111% and the mean is 31% since thedata is obviously skewed to the left (more did well).D. The mean is 111% and the median is 31% since thedata is obviously skewed to the right (more failed).E. The median is 111% and the mean is 31% sincethe data is obviously skewed to the right (more didfailed).15. Suppose age ∼ N (20, 22), which statement BESTequates to P (age10> 22)?A. How likely are we to get an average age greater than22?B. How likely are we to get a sample of 10 with agegreater than 22?C. How likely are we to get 10 samples with age greaterthan 22?D. How likely are we to get 10 samples with an averageage greater than 22?E. How likely are we to get an average age from a sam-ple of 10 greater than 22?16. The first thing you must ALWAYS do when given datato analyze isA. calculate the mean and the standard deviationB. plot the dataC. determine what type of data you’ve been givenD. find any outliers since they will affect the statisticsyou’ll need to calculateE. decide if there could be lurking variables3STAT303 sec 508-510 Exam #1, Form A Spring 201117. Suppose we weigh 50 people. 49 of them are between180 and 280 lbs. One weighs only 150 lbs. Which of thefollowing is true for this


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