STOR 155 Practice Midterm 1 Fall 2009 INSTRUCTIONS BOTH THE EXAM AND THE BUBBLE SHEET WILL BE COLLECTED YOU MUST PRINT YOUR NAME AND SIGN THE HONOR PLEDGE ON THE BUBBLE SHEET YOU MUST BUBBLE IN YOUR NAME YOUR STUDENT IDENTIFICATION NUMBER EACH QUESTION HAS ONLY ONE CORRECT CHOICE decimals may need rounding USE NUMBER 2 PENCIL ONLY DO NOT USE INK FILL BUBBLE COMPLETELY NO NOTES OR REMARKS ARE ACCEPTED DO NOT TEAR OR FOLD THE BUBBLE SHEET A GRADE OF ZERO WILL BE ASSIGNED FOR THE ENTIRE EXAM IF THE BUBBLE SHEET IS NOT FILLED OUT ACCORDING TO THE ABOVE INSTRUCTIONS 1 This is a standard deviation contest Which of the following sets of four numbers has the largest possible standard deviation A 0 0 10 10 B 7 8 9 10 C 0 1 2 3 D 5 5 5 5 2 What interval on the horizontal axis corresponds to the middle 50 of area under the standard Normal density curve A 0 4017 0 5987 B 0 5 0 5 C 0 67 0 67 D 0 25 0 25 3 A stemplot of a set of data is roughly symmetric but the data do not even approximately follow the 68 95 99 7 rule We conclude that the data are A standard normal B normal C normal but they are not standard normal D not normal Page 1 4 Which of the following is likely to have a mean that is smaller than the median A The scores of students out of 100 points on a very difficult exam on which most score poorly but a few do very well B The prices of homes in a large city C The salaries of all National Football League players D The scores of students out of 100 points on a very easy exam in which most score perfectly but a few do very poorly 5 Use the following density curve to answer the question below For this density curve what percent of the observations lie between 0 25 and 1 2 A 47 5 B 52 5 C 95 D 25 Page 2 6 A sample was taken of the salaries of 20 employees of a large company The following are the salaries in thousands of dollars for this year For convenience the data are ordered 28 49 31 51 34 52 35 52 37 60 41 61 42 67 42 72 42 75 47 77 According to corporate policy every employee will receive a 5 pay increase every year This year the company performs really well The CEO decides that each employee in the company will receive a 3000 raise for next year each employee s salary is increased by 3000 in addition to the regular 5 pay increase The standard deviation of the salaries for the employees will A increase by 5 B be multiplied by 5 C be unchanged D change but none of the above is true 7 Consider the following normal quantile plot 20 16 12 8 1 25 0 00 Normal Scores The most striking feature of the plot is A the fact that Y is categorical B the many outliers evident in the plot C the granularity D the strong skewness indicated by the plot Page 3 1 25 8 The mean cholesterol levels of ten men who visited a cholesterol screening clinic located in the downtown area is 250 The nurse later found out that one of the men s cholesterol level should be 230 but was mistakenly recorded as 280 After correcting this recording error the mean cholesterol level in this sample is A 240 B 245 C 255 D impossible to calculate Page 4 9 Each of the following two histograms represents the distribution of acceptance rates percent accepted among 25 business schools in 1995 The histograms use different intervals but are based on the same data In each interval the left endpoint is included but not the right 5 4 3 2 1 10 20 30 40 Acceptance Rate 8 6 4 2 7 5 30 0 52 5 Acceptance Rate What percent of the schools have an acceptance rate of under 20 A 4 B 12 C 16 D 3 Page 5 10 The Insurance Institute for Highway Safety publishes data on the total damage suffered by compact automobiles in a series of controlled low speed collisions A sample of the data in dollars with brand names removed is 950 650 850 750 The interquartile range of the above data is A 400 B 300 C 200 D none of the above 11 A reporter wishes to portray baseball players as overpaid Which measure of center should he report as the average salary of major league players A The median B The mean C Either the mean or median They will be equal in this case D Neither the mean nor the median Both will be much lower than the actual average salary 12 The time to complete a standardized exam is approximately normal with a mean of 70 minutes and a standard deviation of 10 minutes Using the 68 95 99 7 rule what percentage of students will complete the exam in under an hour A 5 B 16 C 68 D 32 13 A local small business has 30 workers 2 3 of which are female The average salary of all female workers is 40 000 The average salary of all male workers is 45 000 What must be true about the average salary of all workers A It must be larger than the median salary B It must be smaller than 42 500 C It must be 42 500 D It could be any number between 40 000 and 45 000 Page 6 14 A set of data has a median that is much larger than the mean Which of the following statements is most consistent with this information A A stemplot of the data is skewed right B A stemplot of the data is symmetric C A stemplot of the data is skewed left D The data set must be so large that it would be better to draw a histogram than a stemplot 15 A soft drink machine can be regulated so that it discharges an average of ounces per cup If the ounces of each discharge are normally distributed with a standard deviation of 0 4 oz what value should be set at so that 6 oz cups will overflow only 2 5 of the time A 5 18 B 5 22 C 6 78 D 6 82 16 A company produces packets of soap powder which are labeled Giant Size 32 oz The actual weight of soap powder in a box has a normal distribution with a mean of 33 oz and a standard deviation of 0 7 oz 95 of packets actually contain more than x ounces of soap powder What is x A 31 60 B 34 40 C 34 15 D 31 85 17 The weights of packets of cookies produced by a certain manufacturer have a normal distribution with a mean of 202 g and a certain standard deviation It is stamped on …
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