Stat303: Statistical MethodsReview for Exam I (07/14/2009)Instructor: Anh Dao1. Boxplots are the best numeric graphs that we have discussed for(A) determining if there are outliers(B) comparing distributions(C) finding the mean(D) All of the above are true.(E) Only two of the above are true.2. Suppose you are trying to see if there is a linear relationship between the two numerical variables,X and Y . You find that the correlation r = 0.006 (or R = 0.006). What can be concluded from this?(A) There is no linear relationship between X and Y .(B) There is a strong linear relationship between X and Y .(C) X and Y are the same variable.(D) There may or may not be a linear relationship between X and Y . You would need to see ascatterplot before coming to a conclusion about the relationship between X and Y .(E) None of the above.3. Suppose your z-score for this exam is 0. This means(A) You didn’t miss any questions.(B) You made the average score.(C) The distribution of the scores is normal.(D) Two of the above are true.(E) None of the above are true.4. Suppose you know that the data you have is normal in shape and the mean, µ = 30, and the standarddeviation, σ = 5. Which of the following would you also know?(A) The minimum would be about 15(B) The IQR would be less than 5(C) The 95th percentile would be more than 40.(D) All of the above are true.(E) Only two of the above are true.5. Figure(1) shows a discrete variable histogram and the numbers at the bottom indicate the values withinthe bins to the right. Which of the following is true?12 Review for Exam I(A) The median is 4 and since the data is skewed to the right, the mean is more than 4.(B) The median is 3 and since the data is skewed to the right, the mean is more than 3.(C) The median is 4 and since the data is skewed to the left, the mean is more than 4.(D) The mean is 4 and since the data is skewed to the right, the median is more than 4.(E) The median is 3 and since the data is skewed to the left, the mean is more than 3.Figure 1: Histogram6. Again referring to the histogram, which of the following statements is/are true?(A) If the minimum, 0, was decreased to -10, the mean and the standard deviation would both increase.(B) Since the range is 8 − 0 = 8, the IQR is 6 − 2 = 4.(C) z-scores cannot be calculated for this data since it’s skewed.(D) Two of the above are true(E) None of the above are true.7. Which of the following is/are true for the data represented in Figure(2)? There are 50 points in each.(A) Although the range of the bottom boxplot is larger than the middle one, the middle one has alarger standard deviation. (Remember the definition of standard deviation).(B) The middle boxplot has the largest mean(C) Only the top boxplot has no outliers.(D) All of the above are true.(E) We need summary numbers to determine any of the above8. The 5-Number Summary for the bottom boxplot is approximately(A) 0, 5, 12, 20, 100(B) 0, 5, 12, 20, 45(C) 0, 5, 12, 15, 20, 45(D) 0, 5, 12, 20, 50Review for Exam I 3Figure 2: Boxplots(E) 0, 5, 12, 20, 42.59. If a Blynn student has a 3.8 grade point, where µ = 3.5 with σ = 0.2 and an Aggie has a 2.9 whereµ = 2.75 with σ = 0.3, who’s doing better, relatively?(A) The Blynn student since they have a higher GP.(B) The Blynn student since their GP is more above their mean (3.8 – 3.5).(C) The Blynn student since their standard deviation is smaller.(D) The Blynn student since their z-score is higher.(E) The Aggie just because!The data below came from a SRS taken from all Americans. It was done General Social Survey ofAmerican’s in 1991 to determine whether an association existed between gender and perception of levelof excitement in life.Table 1: Association between Gender and PerceptionCount Exciteng Routine Dull TotalMale 260 140 12 412Female 221 305 29 555Total 481 445 41 96710. How likely is a Female (given the gender) to think her life is Exciting?(A) 221(B) 221/967(C) 221/555(D) 221/4814 Review for Exam I(E) 481/55511. Do men and women view their life differently in this study?(A) Yes, more men think their life is exciting.(B) Yes, the proportion of men who think their life is exciting is much larger than that for women.(C) We can’t compare since there’s less men than women in the study.(D) No, the proportions are about equal for men and women.(E) None of the above are correct.12. What can be said how the data represented in Fig(3)?(A) Since the data is categorical, we can’t say anything about it.(B) If we made a bar chart: red, white, blue, it would be skewed to the right.(C) There are more red’s than either white’s or blue’s.(D) There are twice as many red’s as blue’s.(E) Two of the above are correct.Figure 3: Pie Chart13. Suppose you know that your data is approximately bell-shaped and the mean is 50 with a standarddeviation of 5. Approximately how much of the data falls between (45, 60)?(A) 47.5%(B) 68%(C) 81.5%(D) 95%(E) 61%14. Describe the correlation in the plot Figure(4).(A) Strongly negative(B) Moderately negativeReview for Exam I 5Figure 4: Scatterplot(C) Weak(D) Moderately positive(E) Strongly positive15. Given the equation of the line is ˆy = −17 + 0.17x. What would happen if the point (300, 35) wereadded to the data above?(A) Nothing would change since the point would be on the line (close)(B) The correlation would be stronger, but the line would not.(C) The line and the correlation would change since the point would be influential.(D) The line wouldn’t change much, but the correlation would decrease since the point would beanoutlier.(E) The line would change, but the correlation would not.16. Using the bivariate data above, which of the following would be correct if you divided all of the X’sby 10 so X and Y would have similar ranges?(A) The mean of X would be about 25.(B) The new slope would be 0.017.(C) The new intercept would be -0.17(D) All of the above are correct.(E) Only two of the above are correct.17. The only statistics that we have discussed that are NOT affected by outliers are(A) the correlation, r, and z-scores(B) the mean and the standard deviation(C) the median and the standard deviation(D) Two of the above are not affected by outliers.6 Review for Exam I(E) None of the above are correct.18. Suppose data was collected from statistics students regarding the length of time they studied for anexam, X, and their grade on the exam, Y . The data contained scores for students that studiedanywhere from 0 to 8 hours. From
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