BUS/ST 350 Final Exam Spring 2012

Transcription

1 BUS/ST 350 Final Exam Spring 2012 Name Lab Section ID # INSTRUCTIONS: Write your name, lab section #, and ID# above. Note the statement at the bottom of this page that you must sign when you are finished with the exam. Supply the following information on SIDE ONE of the scantron sheet: Enter your name (last name first!) in the "name" section; no nicknames! FILL IN THE BUBBLES. Enter your 3 digit lab section number in the "special code" section. FILL IN THE BUBBLES. Enter your student identification number in the "identification number" section. FILL IN THE BUBBLES. IMPORTANT! BUBBLE IN the version number (either "1", "2"or "3") of your copy of the exam in the section marked "GRADE OR EDUCATION". There are 25 multiple choice questions. On the test circle the letter that corresponds to the answer you select. Also indicate your selection on the opscan sheet. Use a #2 pencil! For each wrong answer 4 points will be subtracted from 100. When you are finished: separate your scantron sheet from the test! i) place the 1st page of your test in the proper lab section stack on the auditorium stage ii) place your scantron sheet in the folder labeled with your version of the test. GOOD LUCK!! Statement of academic honesty: I have neither given assistance to another student nor received assistance from another student while taking this exam. Signed 1

2 1) A manufacturer of cheese filled ravioli supplies a pizza restaurant chain. Based on data collected from its automatic filling process, the amount of cheese inserted into the ravioli is normally distributed. To make sure that the automatic filling process is on target, quality control inspectors take a sample of 25 ravioli and measure the weight of cheese filling. They find a sample mean weight of 15 grams with a standard deviation of 1.5 grams. What is the margin of error at 90% confidence? A) 0.3 grams B) 0.06 grams C) grams D) 1.5 grams E) grams 2) Top management at a large software company wishes to estimate the average number of hours its firm's professional employees volunteer in the local community. Based on past similar studies, the standard deviation was found to be 2.22 hours. If top management wants to estimate the average number of hours volunteered per month by their professional staff to within one hour with 99% confidence, how many randomly selected professional employees would they need to sample? A) 44 B) 33 C) 25 D) 19 E) 54 3) Insurance companies track life expectancy information to assist in determining the cost of life insurance policies. Last year the average life expectancy of all policyholders was 77 years. ABI Insurance wants to determine if their clients now have a longer life expectancy, on average, so they randomly sample 20 of their recently paid policies. The sample has a mean of 78.6 years and a standard deviation of 4.48 years. The P-value associated with the resulting test statistic is Which of the following is the correct conclusion? I. We fail to reject the null hypothesis. II. We reject the null hypothesis. III. There is not significant evidence to indicate an increase in average life expectancy. A) III only B) I and III only C) II and III only D) I only E) II only 4) A popular restaurant takes a random sample n = 25 customers and records how long each occupied a table. The found a sample mean of 1.2 hours and a sample standard deviation of 0.3 hours. Find the 95 percent confidence interval for the mean. A) 1.2 ±.609 B) 1.2 ±.118 C) 1.2 ±.588 D) 1.2 ±.124 5) Suppose we want to test H0 : µ = 30 versus HA : µ < 30. Which of the following possible sample results based on a sample of size 36 gives the strongest evidence to reject H0 in favor of HA? A) X = 26, s = 9 B) X = 28, s = 6 C) X = 27, s = 4 D) X = 32, s = 2 6) A major airline is concerned that the waiting time for customers at its ticket counter may be exceeding its target average of 190 seconds. To test this, the company has selected a random sample of 100 customers and times them from when the customer first arrives at the checkout line until he or she is at the counter being served by the ticket agent. The mean time for this sample was 202 seconds with a standard deviation of 28 seconds. What is the correct formula for the calculation of the test statistic for this hypothesis test? A) t = B) t = C) t = / 100 D) t = / 100. E)

3 7) Education and child psychology experts claim that the medication given to children diagnosed with Attention Deficit Hyperactivity Disorder (ADHD) improves academic performance. But many parent organizations, worried about giving young children drugs that can have adverse side-effects, claim that teachers show favoritism toward ADHD children who take medication over ADHD children who do not take medication. To investigate this claim the teachers of 75 ADHD children were told that the children were receiving medication, but the children were actually given a sugar pill. The same teachers were told that 50 different ADHD children were not taking any medication. Grades given to the ADHD students taking sugar pills had mean 85 and standard deviation 7; grades given to the ADHD children not taking any medication had mean 79 and standard deviation 5. A 99% confidence interval for the difference in mean grades between ADHD students taking sugar pills and ADHD students not taking any medication is: (use minimum (n1-1, n2-1) to estimate the degrees of freedom ). A) (85-79) ± B) (85-79) ± C) (85-79) ± D) (85-79) ± E) (85-79) ± ) A relief fund is set up to collect donations for the families affected by recent storms. A random sample of 400 people shows that 28% of those 200 who were contacted by telephone actually made contributions compared to only 18% of the 200 who received first class mail requests. Which formula calculates the 95% confidence interval for the difference in the proportions of people who make donations if contacted by telephone or first class mail? A) ( ) ± 1.96 (0.23)(0.77) 200 B) ( ) ± 1.96 C) ( ) ± 1.96 D) ( ) ± 1.96 E) ( ) ± 1.96 (0.23)(0.77) 200 (0.23)(0.77) 400 (0.28)(0.72) 400 (0.28)(0.72) (0.23)(0.77) (0.18)(0.82) (0.18)(0.82) 200

4 Determine the shape, direction, and strength in the following scatterplot. 9) A) Linear shape, positive association, very strong B) Linear shape, negative association, very strong C) Curved shape, negative association, weak strength D) Oblong shape, Negative association, moderate strength E) Linear shape, negative association, moderate strength 10) When using midterm exam scores to predict a student's final grade in a class, the student would prefer to have a A) negative residual, because that means the student's final grade is higher than we would predict with the model. B) positive residual, because that means the student's final grade is higher than we would predict with the model. C) negative residual, because that means the student's final grade is lower than we would predict with the model. D) positive residual, because that means the student's final grade is lower than we would predict with the model. E) residual equal to zero, because that means the student's final grade is exactly what we would predict with the model.

5 11) In which scatterplot is the correlation r approximately 0.01? a b c d e f A) c B) e C) f D) d E) a 12) The data below are ages and systolic blood pressures (measured in millimeters of mercury) of 9 randomly selected adults. The summary statistics are x = 51, sx = 9.014, y = , sy = , r = Find the equation of the regression line for the given data. What would be the predicted pressure if the age was 60? Round the predicted pressure to the nearest whole number. Age, x Pressure, y A) ^y= 1.488x ; 150 mm B) ^y= 60.46x ; 3626 mm C) ^y= 60.46x ; 3629 mm D) ^y= 1.448x ; 29 mm

6 13) A county real estate appraiser wants to develop a statistical model to predict the appraised value of houses in a section of the county called East Meadow. One of the many variables thought to be an important predictor of appraised value is the number of rooms in the house. Consequently, the appraiser decided to fit the simple ^ linear regression model, y = b0 + b1x, where y = appraised value of the house (in $thousands) and x = number of rooms. Using data collected for a sample of n = 74 houses in East Meadow, the following least squares prediction line was obtained: ^ y= x Give a practical interpretation of the slope of the least squares prediction line. A) For a house with 0 rooms, we estimate the appraised value to be $74,800. B) For each additional room in the house, we estimate the appraised value to increase $22,750. C) For each additional room in the house, we estimate the appraised value to increase $74,800. D) For each additional room in the house, we estimate the appraised value of the house to increase by $22.75 per square foot. ^ 14) The regression line for the given data is y = -2.75x Determine the residual of a data point for which x = 2 and y = 92. Number of absences, x Final grade, y A) B) 1.36 C) D) ) An academic advisor at a top business school wants to predict the typical starting salary of a graduate using the GMAT score of the student as the explanatory variable. With y = salary and x = GMAT score, the least squares ^ prediction line using data from 25 students is y = x with r2 = Give a practical interpretation of r2 = A) We estimate salary to increase $.66 for every 1-point increase in GMAT. B) 66% of the variation in salary is explained by differences in GMAT scores. C) We can predict salary correctly 66% of the time using GMAT scores. D) 66% of the differences in GMAT scores are caused by variation in the salary. 16) Education research consistently shows that students from wealthier families tend to have higher SAT scores. The slope of the line that predicts SAT score from family income is 6.25 points per $1000, and the correlation between the variables is Then the slope of the line that predicts family income from SAT score (in $1000 per point) A) is B) is 6.25 C) is 3.00 D) is E) is ) In a recent survey of drinking laws, a random sample of 1000 women showed that 65% were in favor of increasing the legal drinking age. In a random sample of 1000 men, 60% favored increasing the legal drinking age. Construct a 95% confidence interval for p1 - p2. A) (0.008, 0.092) B) (0.587, 0.912) C) (-2.153, 1.679) D) (-1.423, 1.432)

7 18) Assume the proportion of students retained at a certain university in 2008 is p08 and the proportion of students retained in 2009 is p09. Based on a recent study, a 90% confidence interval for p08 - p09 is ( , ). Give an interpretation of this confidence interval. A) We are 90% confident that the proportion of students retained in 2009 is between 3.98% less and 2.62% more than the proportion of students retained in B) There is a 90% probability that the proportion of students retained in 2009 is between 3.98% less and 2.62% more than the proportion of students retained in C) There is a 90% probability that the proportion of students retained in 2008 is between 3.98% less and 2.62% more than the proportion of students retained in D) We are 90% confident that the proportion of students retained in 2008 is between 3.98% less and 2.62% more than the proportion of students retained in E) If samples were repeatedly drawn from the same populations under the same circumstances, the true population difference (p08 p09) would be between and % of the time. 19) A grocery store is interested in determining whether or not a difference exists between the shelf life of Hot'n Now doughnuts and Sugar Yum doughnuts. A random sample of 100 boxes of each brand was selected and the mean shelf life in days was determined for each brand. A 90% confidence interval for the difference of the means, µhn - µsy, was determined to be (1.1, 2.4). A) Since the values in the confidence interval are positive, the probability that the mean shelf life of Hot'n Now doughnuts is longer than the mean shelf life of Sugar Yum doughnuts is 90%. B) We are 90% confident that the interval (1.1, 2.4) captures the number of days that the mean shelf life of Hot'n Now doughnuts exceeds the mean shelf life of Sugar Yum doughnuts. C) There is a 90% chance that a randomly selected box of Hot'n Now doughnuts will have a shelf life that is between 1.1 and 2.4 days longer than a randomly selected box of Sugar Yum doughnuts. D) Since the values in the confidence interval are positive, the probability that the mean shelf life of Sugar Yum doughnuts is longer than the mean shelf life of Hot'n Now doughnuts is 90%. E) We are 90% confident that the interval (1.1, 2.4) captures the number of days that the mean shelf life of Sugar Yum doughnuts exceeds the mean shelf life of Hot'n Now doughnuts. 20) Among the possible lines that can go through data points in a scatterplot, the regression line results from the least squares method and has the smallest value for the. A) intercept B) residual sum of squares C) residual sum D) correlation E) slope 21) A major retail clothing store is interested in estimating the difference in mean monthly purchases by customers who use the store's in-house credit card versus using a Visa, Mastercard, or one of the other major credit cards. To do this, they have randomly selected a sample of customers who have made one or more purchases with each of the types of credit cards. The following represents the results of the sampling: In-House Credit Card National Credit Card Sample Size: Mean Monthly Purchases: $45.67 $39.87 Standard Deviation: $10.90 $12.47 Based on these sample data, what is the lower bound for the 95 percent confidence interval for the difference between population means? (Use min(n1-1, n2-1) for the degrees of freedom) A) Approximately $2.58 B) Approximately $3.41 C) About $5.28 D) Approximately $4.85

8 22) The regression equation that relates a student's weight to the number of hours spent on the computer, x1, the number of hours viewing television, x2, and the number of hours on their cell phone, x3, per day is ^ y = x x x3. What is a student's expected weight change if the amount of television is increased by 1 hour, with the number of hours on the computer and talking on their cell phone held constant? A) 3.26 pounds B) pounds C) 1.75 pounds D) 4.27 pounds 23) A multiple regression is shown for a data set of yachts where the dependent variable is the price in thousands of dollars. Given this information, which of the following is true regarding the slope coefficient for Age, where Age represents how many years old the yacht is? A) On average the price of the yacht falls by $1778 per year B) On average the yacht is years older per $1000 price change C) On average the price of the yacht increases by $1778 per year D) On average the price of the yacht falls by $1.778 per year

9 24) The editors of a national automotive magazine recently studied 30 different automobiles sold in the United States with the intent of seeing whether they could develop a multiple regression model to explain the variation in highway miles per gallon. A number of different independent variables were collected. The following regression output (with some values missing) was recently presented to the editors by the magazine's analysts: Based on this output and your understanding of multiple regression analysis, what percentage of variation in the dependent variable is explained by the regression model? A) approximately 37% B) over 90 % C) approximately 82% D) approximately 89.9% E) approximately 95%

10 25) Linear regression was used to describe the trend in world population over time. Below is a plot of the residuals. What does the plot of residuals suggest? A) The explanatory variable x is useful for predicting y. B) The data are not normal. C) A linear model is not appropriate. D) The roles of x and y as explanatory and response variables should be reversed. E) An outlier is present in the data set.

11 ANSWERS 1. E. 2. B 3. B 4. D 5. C 6. D 7. D 8. E 9. B 10. B 11. B 12. A 13. B 14. B 15. B 16. D 17. A 18. D 19. B 20. B 21. A 22. D 23. A 24. C 25. C

12 TABLE Z Areas under the standard Normal curve z 0 Second Decimal Place in z z

13 TABLE Z Areas under the standard Normal curve 0 z Second Decimal Place in z z

14 Conf. Level 10% 30% 50% 70% 80% 90% 95% 98% 99% Two Tail One Tail df Values of t

15 Conf. Level 10% 30% 50% 70% 80% 90% 95% 98% 99% Two Tail One Tail

16 Conf. Level 10% 30% 50% 70% 80% 90% 95% 98% 99% Two Tail One Tail