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TAMU STAT 303 - ex1asp98

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STAT303: 507-509 Exam #1, Form A Spring 19981. Consider the points represented in the scatter-plot above. How could we make it appear that xand y are less linearly related?A. divide all of the y’s by 10, which would de-crease the slopeB. divide all of the x’s by 10, which would de-crease the slopeC. add another point directly on the lineD. Any of the above would make the relation-ship appear less linear.E. None of the above would change the rela-tionship.2. If the point (15,100) were added to the datasetabove, which of the following would be effected?A. Pearson’s correlation coefficient, r,woulddecreaseB. Spearman’s correlation coefficient, rs,would decreaseC. the slope, would decrease greatlyD. all of the aboveE. exactly two of the above (excluding D.)3. Let Z ∼ N(0, 12). What is P (1.45 <Z<2.45)?A. 1.00B. 0.9929C. 0.9265D. 0.0664E. 0.004. Let X ∼ N(20, 22). What is P (15 <X<25)?A. 0.9876B. 0.0062C. 2.5D. 10E. 0.99385. Let X ∼ N(2, 42). What is x∗such that P (X>x∗)=0.70?A. 0.525B. -0.525C. 0.7580D. 4.1E. -0.1--------------------------------X |-1|0|2|3--------------------------------p(X) | 0.1 | 0.3 | 0.5 | 0.1--------------------------------6. What are the mean, µX, and standard deviation,σX, of the population represented above?A. µX=1.2,σX=3B. µX=1.2,σX=1.25C. µX=1.2,σX=1.56D. µX=2,σX=1.56E. µX=2,σX=37. What is the median of the population repre-sented above?A. It can’t be determined from the table above.B. The population is skewed to the left, so themedian must be to the left (smaller) thanthe mean.C. The population is skewed to the right, sothe median must be to the left (smaller)than the mean.D. The population is skewed to the left, so themedian must be to the right (larger) thanthe mean.E. The population is skewed to the right, sothe median must be to the right (larger)than the mean.8. How can you determine if two events, A and B,are independent?A. If P (A and B) = 0, they are independent.B. If P (A and B)=P(A)∗P(B), they areindependent.C. If P (A or B) = 0, they are independent.D. If P (A or B)=P(A)∗P(B), they are in-dependent.E. If P (A) ∗ P (B) = 0, they are independent.2STAT303: 507-509 Exam #1, Form A Spring 19989. If you are trying to decide how well you are doingin class compared to your friend who is takingSTAT302, what statistic should you compare?It’s known that STAT302 has a lower averagethan STAT303.A. You can’t compare grades since the meansare different.B. You should compare z-scores since thatwould take care of the different means.C. You just need to look at the first test scoressince that’s the best indicator of how youare doing in the class.D. You should compare your test averages atthe end of the semester since that’s how thegrades are determined.E. You should compare your GPR’s sincethat’s what goes on record.10. Looking at the boxplots above, which of thedatasets most likely has the largest standarddeviation? Remember: standard deviation is ameasure of spread.A. 1B. 2C. 3D. 5E. 6Percentiles Smallest1% -3.54784 -3.547845% -3.214333 -3.21433310% -3.099243 -3.1288325% -2.805166 -3.06965650% -2.20806Largest75% -.89802 .793719390% 1.236699 1.67967995% 2.20186 2.2018699% 2.669803 2.66980311. Which of the boxplots is represented by the out-put above?A. 2B. 3C. 4D. 5E. 612. Which of the boxplots is most likely representedby the histogram above?A. 1B. 2C. 3D. 4E. 513. Let Z ∼ N (0, 12). What is Q3, the 75th per-centile of Z, i.e.,whatisz∗such that P (−z∗ <Z<z∗)=0.50?A. 0.00B. 0.675C. 0.6915D. 0.75E. 0.773414. Let X ∼ N(10, 22). What is the distribution ofthesamplemean,X16, for samples of size n =16?A. The mean, µX, will be 10, but the distribu-tion and variance can’t be determined.B. The mean, µX, will be 10 and the vari-ance, σX, will be 22, but the distributionand variance can’t be determined.C. X16∼ N(10, 22)D. X16∼ N(10, 22/16)E. X16∼ N(10, 22/4)3STAT303: 507-509 Exam #1, Form A Spring 199815. Which of the scatterplots above shows thestrongest linear correlation?A. 1B. 2C. 3D. 4E. You need a regression line to determine thelinearity.16. Let X ∼ N(10, 22)andY =∼N(9, 42). Whatare the mean and standard deviation of X − Yif X and Y are independent?A. µX−Y= 19, σX−Y=6B. µX−Y=1,σX−Y=−2C. µX−Y=1,σX−Y=4.5D. µX−Y=1,σX−Y=2.4E. µX−Y= 19, σX−Y=2.4R-squared = 0.8827----------------------------------demand | Coef. Std. Err.---------+-----------------------supply | 9.00 .6205413_cons | 19.60 9.218746----------------------------------17. What is the predicted value for demand whensupply = 15?A. 303.0B. -115.4C. 154.6D. 115.4E. 285.018. Which of the following is false?A. A subset of a population is called a statistic.B. A simple random sample of size n is a sam-ple that is selected in such a way that everypossible sample of size n is equally likely tobe chosen.C. A dataset is called catagorical if the obser-vations are qualitative responses.D. Two of the above are false statements.E. All of the above are true statements.19. Which of the following indicate that the data isnormally distributed?A. a bell-shaped histogramB. a straight line normal quantile plotC. a symmetric boxplotD. all of the aboveE. exactly two of the above20. What percent of the observations in the datasetrepresented above will fall within 2 standard de-viations of the mean?A. exactly 95%B. exactly 75%C. about 95%D. no more than 75%E. at least 75%21. Again referring to the dataset represented above,which of the following would change if we multi-plied each observation by 5?A. the mean, but not the medianB. the standard deviationC. the z-scoresD. All of the above are correct.E. Only two of the above are correct.4STAT303: 507-509 Exam #1, Form A Spring 1998Answers: 1. A 2. E 3. D 4. A 5. E 6. B 7. D 8. B9. B 10. A 11. A 12. D 13. B 14. D 15. A 16. C 17. C18. A 19. E 20. E 21.


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